Dual-mode shared OFDM methods/transmitters, receivers and systems

Dual-mode shared OFDM method/transmitter, receiver and system

FIELD OF THE INVENTION The present invention generally relates to wireless communication, in particular, to an uplink air interface used in a wireless communication network, and more particularly, to a dual-mode shared OFDM method/transmitter, receiver, and system.

Background A wireless network usually includes an access point (such as a base station) through which a user equipment (UE) can access the wireless network. Each access point generally serves a roughly defined geographic area called a coverage area, in which a UE can be used to establish a wireless link with a specific access point. In other words, in the coverage area corresponding to the access point, the UE can generally be expected to be able to perform wireless communication (transmit and receive signals) with the corresponding access point.

Generally, transmissions initiated from one or more UEs and sent to the access point are collectively referred to as uplink (to the access point). This is an example of a many-to-one communication system in which multiple UEs must share access to a common wireless channel. Since it is not easy to synchronize transmissions initiated from different UEs in an actual environment, it is difficult to manage the access of multiple users to the public wireless channel. Specifically, in a cellular network, the uplink consists of many point-to-point transmissions, all of which are directed to the base station (access point) and are initiated from various UEs operating in the cell (coverage area) served by the base station.

Must specify and follow the access scheme commonly referred to as the uplink air interface to control how each UE in the wireless communication network sends signals to the access point (e.g., base station) so that multiple UEs can effectively share the common radio channel . In a cellular network, the uplink air interface must consider the transmission of multiple UEs working in the same cell and the transmission of UEs working in neighboring cells. In other words, to make wireless communication effective, a method of dividing public wireless channels, also known as channelization, must be applied, so that each UE can obtain transmission access to a certain part of the public wireless channel within a reasonable time.

Different multi-user access schemes have been developed and used for the uplink air interface in cellular networks. Examples of such multi-user access schemes include channelization based on the following factors: i) frequency division; ii) time division; and iii) code division. According to Frequency Division Multiple Access (FDMA), a common wireless channel is divided into multiple sub-channels, and each sub-channel can be dedicated to a single UE. On the other hand, basic time division multiple access (TDMA) allows multiple users to transmit on the entire public wireless channel one user at a time. Code Division Multiple Access (CDMA) allows multiple UEs to transmit in the entire public radio channel at the same time by assigning a unique spreading code (cover code) to each UE. This spreading code is the same as that for other UEs. All other spreading codes assigned are orthogonal. In other words, a spreading code (cover code) is used as an identifier or a cover code included in each UE's respective transmission.

The maximum data rate associated with the uplink transmission of each of the above schemes is limited. For example, in a 3G (ie, third generation) cellular network, based on CDMA, the inherent multiple access interference of CDMA limits the data rate transmission to 2 Mbps. In addition, since different UEs generally cannot send signals synchronously, it is difficult to maintain the orthogonality provided by each allocated spreading code between transmissions of different UEs. Once the orthogonality between different UE transmissions is compromised, multiple access interference will occur, which limits the maximum uplink data rate. Generally, in a cellular network, all multiple access interference can be composed of intra-cell and inter-cell multiple access interference.

European digital audio broadcasting services and some WLAN (Wireless Local Area Network) uplink access schemes use a modulation technique called Orthogonal Frequency Division Modulation (OFDM). OFDM is also suitable for digital television and is being considered as a method to obtain high-speed digital data transmission on conventional telephone lines. Advantageously, OFDM allows simple processing to prevent dispersive channel distortion and high-speed data rate transmission in a broadcast environment and single point-to-point communication. The disadvantage of OFDM is that although it is effective for broadcast and single point-to-point communication, it is essentially not considered for multi-user access.

OFDM has been combined with time division multiplexing (TDM) in systems that require multi-user access. For example, in some WLAN networks, OFDM is combined with TDM to provide multiple access capabilities. In other words, OFDM is used for uplink transmission from one user at a time, and multi-user access is arranged in a TDM manner. However, this type of uplink access scheme cannot effectively support cellular network deployment and mobility because it does not provide the quality of service and functions required in cellular networks. In addition, these solutions do not support circuit data services such as voice.

SUMMARY OF THE INVENTION According to a broad aspect, the present invention provides a wireless terminal that communicates by sharing an OFDM frequency band, the wireless terminal including: a device for generating and transmitting a low-rate mode OFDM transmission in a first frequency band of the OFDM frequency band A first transmission chain; a second transmission chain for generating and sending burst mode transmission in a second frequency band of the OFDM frequency band, the first frequency band being different from the second frequency band.

In some embodiments, the first transmission chain is power controlled and the second transmission chain is rate controlled.

According to another broad aspect, the present invention provides a wireless terminal that communicates by sharing an OFDM frequency band, the wireless terminal including: a first frequency band for generating and transmitting a low-rate mode OFDM transmission in a first frequency band of the OFDM frequency band. A transmission chain; the first transmission chain includes a hopping pattern generator that causes the first frequency band to hop near frequencies within the shared OFDFM frequency band subset allocated for low-rate mode OFDM transmission.

In some embodiments, the first transmission chain includes a space-time encoder adapted to perform space-time coding to generate a signal sent as the low-rate mode OFDM transmission during each OFDM transmission interval.

In some embodiments, the wireless terminal includes N transmit antennas, N>=2, wherein: the first transmission chain includes a space-time encoder, which is adapted to perform space-time coding to generate corresponding STC (space-time Encoding) sub-blocks, the STC sub-blocks include symbols of N transmission intervals to be transmitted as the low-rate mode OFDM transmission on each transmitting antenna during each group of N OFDM transmission intervals multiplied by M sub-carriers.

In some embodiments, the first transmission chain includes a hopping pattern generator that causes the first frequency band to hop around frequencies within the shared OFDM frequency band subset allocated for low-rate mode OFDM transmission And wherein: the jump mode generating jump unit is equal to the jump of the STC block size.

In some embodiments, each STC sub-block also includes pilot symbols.

In some embodiments, each STC sub-block further includes N pilot symbols on a corresponding single sub-carrier at each end of the STC sub-block.

In some embodiments, the first transmission chain further includes: at least one low-rate signal source; at least one different orthogonal spreading function corresponding to each low-rate signal source, adapted to multiply the symbol by the positive The corresponding orthogonal spreading function in the cross-spreading function set generates a corresponding spreading sequence for each symbol of the low-rate signal source; it is used to add the spreading sequences together in time to generate the The combiner of the composite sequence sent in the first frequency band.

In some embodiments, the wireless terminal includes N transmit antennas, N>=2, wherein: the first transmission chain includes a space-time encoder, which is adapted to perform space-time encoding to generate corresponding STC sub-blocks, The STC sub-block includes M symbols of several subcarriers in N transmission intervals to be sent as the low-rate mode OFDM transmission on each transmit antenna during each group of N OFDM transmission intervals, wherein: the composite sequence Input to the space-time encoder.

In some embodiments, the set of orthogonal spreading functions includes Walsh codes.

In some embodiments, the at least one low-rate signal source includes at least one of the following: DL (downlink) channel condition (CQI/CLI) feedback channel; DL ACK/NAK signaling channel; UL (uplink) Buffer status channel; UL transmit power range channel; UL rate indicator channel; UL fixed data rate dedicated service channel.

In some embodiments, the wireless terminal is further adapted to apply an indefinite number of Walsh code channels to the at least one low-rate signal source according to the required data rate and/or protection requirements.

In some embodiments, the wireless terminal further includes: a control channel receiver for receiving a power control command related to the low-rate mode OFDM transmission; Power control function of transmission power adjustment for transmission applications.

In some embodiments, the wireless terminal further includes a function control function adapted to: send an initial access attempt on the uplink access channel; determine a long-term estimate of the signal received over the downlink channel Downlink power measurement value, and initially transmit the low-rate mode OFDM transmission at a transmit power determined according to the estimated downlink power measurement value; the wireless terminal further includes a power control command for receiving power control commands in the initial A power control receiver that increases/maintains/decreases the transmission power of the low-rate mode OFDM transmission after the access attempt.

In some embodiments, the wireless terminal further includes a control channel receiver for receiving channel allocation information to allow identification of the frequency and time at which the low-rate mode OFDM transmission is sent.

In some embodiments, the wireless terminal further includes a control channel receiver for receiving channel allocation information to allow identification of the frequency and time for sending the low-rate mode OFDM transmission, wherein: the channel allocation information includes a hopping pattern The identification allows the wireless terminal to perform hopping according to one mode in the orthogonal hopping mode set.

In some embodiments, the wireless terminal further includes: a coverage code generator for applying cell-specific coverage codes in generating all low-rate mode OFDM transmissions.

In some embodiments, the wireless terminal further includes: at least one channel encoder, which is adapted to apply channel encoding to the low-rate signal source before forming the STC block.

In some embodiments, the channel encoder has a block size including several hops to achieve diversity gain and inter-cell interference averaging.

In some embodiments, the STC block size is NxM plus pilot carrier, where M makes the block size smaller than the coherence bandwidth.

In some embodiments, the wireless terminal further includes: an access channel transmission chain adapted to generate an OFDM access signal occupying a time slot randomly selected from a plurality of time slots including a frame, each time slot including A predetermined block of OFDM time and frequency.

In some embodiments, the wireless terminal further includes: a control channel receiver for receiving multiple feature definition identifiers for use in a coverage area; wherein: the wireless terminal randomly selects one of the multiple features and generates The feature is applied during the access attempt.

In some embodiments, each slot includes 4 OFDM symbols, and there are 16 different possible characteristics.

In some embodiments, the wireless terminal is further adapted to map the feature to the OFDM carrier according to the Peano-Hilbert plane filling curve.

In some embodiments, the access channel is superimposed on the low-rate mode OFDM transmission of other wireless terminals.

In some embodiments, the wireless terminal is adapted to operate in active and standby states, and the wireless terminal further includes: a control channel receiver for receiving system access channel allocation information after entering the standby state, and The system access channel allocation is associated with specific subcarriers and OFDM symbols to be used as the system access channel; wherein: the wireless terminal is also adapted to use the system access channel to send pilots and system access when in a standby state. Incoming request.

In some embodiments, the system access channel includes two or more subcarriers allocated during certain periodic OFDM symbol periods.

In some embodiments, the system access channel is used to send a differentially coded access request, and the access request includes at least one state indicating that a low-rate mode and/or a burst mode capacity request is to be scheduled.

In some embodiments, the wireless terminal further includes a second transmission chain for generating and transmitting a burst mode OFDM transmission that occupies an allocated space in the OFDM frequency and time.

In some embodiments, the second transmission chain includes a space-time encoder adapted to perform space-time coding to generate a signal to be sent as the burst mode OFDM transmission during a plurality of OFDM transmission intervals.

In some embodiments, the wireless terminal includes N transmit antennas, N>=2, wherein: the second transmission chain includes a space-time encoder, which is adapted to perform space-time coding to transmit multiple allocated STC sub-blocks Each position of the frequency-time position generates a corresponding STC sub-block to be transmitted on each transmit antenna.

In some embodiments, each STC sub-block also includes pilot symbols.

In some embodiments, each STC sub-block further includes N pilot symbols at each end of the STC sub-block on a corresponding single OFDM sub-carrier.

In some embodiments, the wireless terminal further includes a control channel receiver for receiving a downlink signaling channel containing burst mode transmission instructions.

In some embodiments, the instruction includes the definition of the transmission frequency and time space of the allocated STC sub-block and coding/modulation primitives.

In some embodiments, the instructions further include a rate control command, and the wireless terminal is adapted to change the coding/modulation primitive according to the rate control command.

In some embodiments, the wireless terminal is further adapted to: measure the long-term power intensity at the serving transmitter; and set the encoding/modulation by using multi-level progressive encoding and modulation feedforward transmission.

In some embodiments, the second transmission chain includes a generated hopping pattern that defines the allocated STC sub-block transmission frequency and time position so that they are within the shared OFDM frequency band subset allocated for burst mode services Jump around the frequency.

In some embodiments, the wireless terminal further includes: an access channel transmission chain adapted to generate an OFDM access signal occupying a time slot randomly selected from a plurality of time slots including a frame, each time slot including A predetermined block of OFDM time and frequency.

In some embodiments, the wireless terminal is adapted to operate in active and standby states, and further includes: a control channel receiver for receiving the system access channel allocation after entering the standby state, the system access channel allocation It is associated with specific subcarriers and OFDM symbols to be used as a system access channel; wherein: the wireless terminal is also adapted to use the system access channel to send pilots and system access requests when in a standby state.

In some embodiments, the wireless terminal is adapted to operate in active and standby states, and further includes: a control channel receiver for receiving the system access channel allocation after entering the standby state, the system access channel allocation It is associated with specific subcarriers and OFDM symbols to be used as a system access channel; wherein: the wireless terminal is also adapted to use the system access channel to send pilots and system access requests when in a standby state.

According to another broad aspect, the present invention provides a wireless terminal for communicating by sharing an OFDM frequency band, the wireless terminal comprising: an access channel transmission chain adapted to generate an occupancy randomly selected from a plurality of time slots including a frame An OFDM access signal for one slot, each slot includes a predetermined block of OFDM time and frequency.

In some embodiments, the wireless terminal further includes: a control channel receiver for receiving multiple feature definition identifiers for use in a coverage area; wherein: the wireless terminal randomly selects one of the multiple features and generates The feature is applied during the access attempt.

In some embodiments, each slot includes 4 OFDM symbols, and there are 16 different possible characteristics.

In some embodiments, the wireless terminal is further adapted to map the feature to the OFDM carrier according to the Peano-Hilbert plane filling curve.

In some embodiments, the access channel is superimposed on the low-rate mode OFDM transmission of other wireless terminals.

In some embodiments, the wireless terminal is adapted to operate in active and standby states, and further includes: a control channel receiver for receiving the system access channel allocation after entering the standby state, the system access channel allocation It is associated with specific subcarriers and OFDM symbols to be used as a system access channel; wherein: the wireless terminal is also adapted to use the system access channel to send pilots and system access requests when in a standby state.

In some embodiments, the system access channel includes two or more subcarriers allocated during certain periodic OFDM symbol periods.

In some embodiments, the system access channel is used to send a differentially coded access request, the request including at least one status indicating that a low rate mode and/or burst mode capacity request is to be scheduled.

In some embodiments, the wireless terminal further includes: a second transmission chain for generating and transmitting burst mode OFDM transmission and transmission occupying the allocated space in the OFDM frequency and time.

In some embodiments, the second transmission chain includes a space-time encoder adapted to perform space-time coding to generate a signal to be sent as the burst mode OFDM transmission during a plurality of OFDM transmission intervals.

In some embodiments, the wireless terminal includes N transmit antennas, N>=2, wherein: the second transmission chain includes a space-time encoder, which is adapted to perform space-time coding to transmit multiple allocated STC sub-blocks Each position of the frequency-time position generates a corresponding STC sub-block to be transmitted on each transmit antenna.

In some embodiments, each STC sub-block also includes pilot symbols.

In some embodiments, each STC sub-block further includes N pilot symbols at each end of the STC sub-block on a corresponding single OFDM sub-carrier.

In some embodiments, the wireless terminal further includes a control channel receiver for receiving a downlink signaling channel containing burst mode transmission instructions.

In some embodiments, the instruction includes the definition of the transmission frequency and time position of the allocated STC sub-block and coding/modulation primitives.

In some embodiments, the instructions further include a rate control command, and the wireless terminal is adapted to change the coding/modulation primitive according to the rate control command.

In some embodiments, the wireless terminal is further adapted to: measure the long-term power intensity at the serving transmitter; and set the encoding/modulation by using multi-level progressive encoding and modulation feedforward transmission.

In some embodiments, the second transmission chain includes a generated hopping pattern that defines the transmission frequency and time position of the allocated STC sub-blocks so that they are in the shared OFDM frequency band subset allocated for burst mode services. Jump around the frequency within.

According to another broad aspect, the present invention provides a network terminal for receiving communications through a shared OFDM frequency band, the network terminal comprising: for receiving burst mode OFDM transmission through a first subset of the shared OFDM frequency band and through shared The second subset of the OFDM frequency band receives low-rate mode OFDM transmission receivers.

In some embodiments, the network terminal is further adapted to extract burst mode OFDM transmissions of multiple wireless terminals from the first subset and extract low-rate mode OFDM transmissions of multiple wireless terminals from the second subset.

In some embodiments, the network terminal further includes: a control channel output for controlling the frequency and time position of the wireless terminal to transmit its low-rate mode transmission.

In some embodiments, the control channel determines a corresponding orthogonal hopping mode for low-rate mode OFDM transmission for each wireless terminal.

In some embodiments, the network terminal further includes: a function control function, which is adapted to determine the low-rate mode OFDM transmission quality of each wireless terminal that sends low-rate OFDM transmission, and to provide a low-rate mode OFDM transmission quality for each wireless terminal that sends low-rate OFDM transmission. Sending a power control signal related to the low-rate mode OFDM transmission.

In some embodiments, the network terminal is further adapted to: for each wireless terminal in a standby state, allocate a corresponding system access channel and send the identification of the corresponding system access channel through the control channel; the network terminal is also suitable To monitor whether the system access channel has a capacity request from the wireless terminal in the standby state.

In some embodiments, the network terminal is further adapted to use the system access channel to maintain timing and synchronization for the wireless terminal in the standby state.

In some embodiments, the capacity request may be a burst mode or low rate mode capacity request.

In some embodiments, the network terminal further includes a control channel output for controlling which wireless terminals will send burst mode OFDM transmissions.

In some embodiments, the control channel output determines the frequency and time at which the burst mode OFDM transmission is to be sent for each wireless terminal that is to send the burst mode OFDM transmission.

In some embodiments, the network terminal is further adapted to perform adaptive rate control on the burst mode transmission.

In some embodiments, the network terminal is further adapted to monitor a random access channel, the random access channel includes: a plurality of time slots, each time slot includes a plurality of OFDM symbol widths, and for each time slot includes M features so that M access attempts can be received within a time slot that is superimposed on the transmission of the active wireless terminal.

In some embodiments, the network terminal is further adapted to send the identification of the feature for use on the random access channel.

In some embodiments, the network terminal is further adapted to grant system access based on an access attempt detected on the random access channel.

According to another broad aspect of the present invention, the present invention provides a system including: a plurality of wireless terminals, wherein each wireless terminal is assigned a corresponding Walsh code, and each user data element generated by the wireless terminal It is extended in time to send on corresponding subcarriers on multiple OFDM symbols, and multiple wireless terminals simultaneously send corresponding data elements on the same subcarrier.

According to another broad aspect, the present invention provides a system including a plurality of wireless terminals, wherein: for a given wireless terminal, for each channel of the wireless terminal, at least one channel is assigned a Walsh code, and any wireless terminal Each user data element of the terminal is transmitted on the OFDM symbol sub-band spread on multiple OFDM sub-carriers, and multiple wireless terminals are simultaneously transmitted on the same OFDM symbol sub-band.

According to another broad aspect, the present invention provides a method of communicating by sharing an OFDM frequency band, which includes: generating and transmitting a low-rate mode OFDM transmission in a first frequency band of the OFDM frequency band; and in a second frequency band of the OFDFM frequency band Burst mode transmissions are generated and sent in; the first frequency band is different from the second frequency band.

In some embodiments, the method further includes: receiving a power control command, and controlling the transmit power of the low-rate mode OFDM transmission according to the power control command; receiving a rate control command and controlling the rate control command according to the rate control command. The transmission rate of burst mode OFDM transmission.

Other aspects of the present invention provide corresponding methods, which are suitable for implementing the method of transmitting/receiving/controlling performed by any wireless terminal or base station outlined above.

Other aspects of the present invention provide a corresponding system that includes a series of combinations of any of the base stations outlined above and a series of many of any of the wireless terminals outlined above.

Other aspects of the present invention provide a corresponding computer-readable medium on which instructions are stored for executing the transmission/reception/control method performed by any wireless terminal or base station outlined above.

By reading the following description of specific embodiments of the present invention, those skilled in the art will understand other aspects and features of the present invention.

Brief Description of the Drawings Fig. 1 is a system block diagram of an OFDMA system provided by an embodiment of the present invention; Fig. 2 shows an example time-frequency resource allocation in a public wireless channel according to an embodiment of the present invention; Fig. 4 is an example time-frequency diagram of mode 1 transmission for a single user; Fig. 5 is an example time-frequency diagram of mode 1 transmission for multiple users; Figs. 6A and 6B are multi-user transmission signal chain block diagrams; An example of other time-frequency diagrams of the users mode 1 transmission; Fig. 7 is an example of multi-user mode 1 transmission using orthogonal Walsh codes instead of STC sub-block separation, where the expansion is performed in the frequency domain; Fig. 8 is an orthogonal Walsh code and An example of non-STC sub-block-separated multi-user mode 1 transmission, where the expansion is performed in the time domain; Figure 9 is an example of how to define RACH time slots according to an embodiment of the present invention; Figure 10A is a diagram showing the combination of RACH and mode 1 frequency space Transmitter block diagram of the mode 1 channel; Fig. 10B is another example transmitter design similar to Fig. 10A, but in which the sub-blocks are encoded; Fig. 11 is a flowchart of the joint RACH detection and uplink synchronization method; Fig. 12 Is an example time-frequency diagram illustrating OFDM subcarrier allocation for an example of mode 2 operation; FIG. 13 is a block diagram of an example transmitter for mode 2 operation; FIG. 14 is a flowchart of an example method for uplink rate control; FIG. 15A is how to combine Example block diagrams of Mode 1 and Mode 2 signals; and Figure 15B shows an example of how to combine Mode 1 and Mode 2 signals in frequency and time.

Detailed description of the preferred embodiment In order to reduce multiple access interference to improve the spectrum efficiency and high data rate limitation in the public wireless channel, a method and device for uplink multi-user access are provided. The methods and devices disclosed herein are based on Orthogonal Frequency Division Modulation (OFDM), and are suitable for providing an effective uplink multi-user access scheme that can be used in wireless communication networks. Therefore, in this article, the OFDM-based uplink multi-user access scheme provided by the present invention will be referred to simply as OFDMA (Orthogonal Frequency Division Multiple Access).

Provides all the uplink operation design, including: uplink establishment; multiple access scheme; uplink channel definition; pilot structure; synchronization strategy; coded modulation scheme; and OFDM resource allocation strategy.

It is conceivable to implement an embodiment characterized by combining one or more or all of the above-mentioned elements.

The basic concept of OFDMA now refers to FIG. 2, which shows an example time-frequency resource allocation formed according to an OFDMA scheme provided by an embodiment of the present invention.

The modulation technique used in OFDMA is OFDM. OFDM is a digital modulation method in which a set of data is mapped onto a set of OFDM subcarriers. Each circle in FIG. 2, for example, the circle identified as 99 represents the transmission of a single subcarrier during the transmission of a single OFDM symbol. Therefore, the horizontal axis in Figure 2 represents frequency, while the vertical axis represents time, and time increases down the page. In the example shown, the OFDM frequency band is shown to contain 32 subcarriers. It is understood that this is only an example, and any suitable number of subcarriers may be used. The number can be very large, for example 1024. This is a simplified diagram, however, where the actual frequency response associated with each subcarrier basically overlaps. However, with OFDM, the frequency response of each subcarrier is designed to be orthogonal to the frequency response of each other subcarrier, so as to allow the data modulated on each subcarrier to be recovered separately at the receiver.

Note that in conventional OFDM, OFDM symbols are defined as consisting of simultaneous transmissions on the entire set of orthogonal subcarriers that determine the OFDM channel. OFDM symbols are sent from a single source to a destination.

According to the OFDMA scheme provided by the embodiment of the present invention, the common wireless channel 50 is implemented using the OFDM transmission scheme in the entire OFDM frequency band. However, within a given symbol duration, the entire OFDM frequency band is not used for a single transmitter, but the OFDM frequency band is divided into two frequency bands 51 and 53 that can be used interchangeably to provide two different types provided by the embodiments of the present invention. OFDMA mode. The two different OFDMA modes are generally referred to herein as Mode 1 and Mode 2, respectively. In the legend, the subcarriers used for mode 1 are generally represented by 60, and the subcarriers used for mode 2 are generally represented by 62. The first frequency band 51 has a first group of 16 subcarriers of the OFDM frequency band 50, and the second frequency band 53 has a second group of 16 subcarriers of the OFDM carrier. The details of Mode 1 and Mode 2 will be discussed separately below. Mode 1 is best to use orthogonal codes to distinguish multiple users simultaneously to provide low-rate circuit-oriented connections, while Mode 2 is used to provide higher-rate burst packet connections.

Figure 2 shows an example of time-frequency resource allocation for Mode 1 and Mode 2 over time. For symbol periods ti to ti+9, the first allocation method is shown, in which the first frequency band 51 is allocated to the mode 1 service, and the second frequency band 53 is allocated to the mode 2 service. Within the symbol duration ti+10, ti+11, the entire OFDM frequency band 50 is dedicated to mode 2 services. Finally, during the symbol duration ti+10 and thereafter, the first frequency band 51 is allocated to the mode 2 service, and the second frequency band 53 is allocated to the mode 1 service. It should be noted that only because the frequency bands are equal to each other in this example, the sizes of the first and second frequency bands 51, 53 do not change over time. For example, if 10 subcarriers are allocated to the mode 1 service and 22 subcarriers are allocated to the mode 2 service, the frequency demarcation point 55 between the two frequency bands will move when the mode 1 service and the mode 2 service are switched.

In the illustrated example, the division of the OFDM frequency band 50 between the frequency bands 51 and 53 is equal, with 16 subcarriers in each frequency band. In one embodiment, the mode 1 and mode 2 time-frequency resource allocation 100 illustrated in FIG. 2 may be the same on the wireless network, and the same allocation occurs in multiple cells. In another embodiment, the time-frequency resource allocation (for mode 1 and mode 2) can be different from cell to cell and time to time. For example, network administrators or individual base stations can dynamically reconfigure resource allocation. In other words, there is no restriction that the corresponding bandwidth allocated for Mode 1 and Mode 2 must be equal. In some embodiments, dividing the OFDM band 50 into bands 51, 53 is a static division. In another embodiment, the division of OFDM frequency band 50 between frequency bands 51 and 53 is based on the traffic load balancing between mode 1 and mode 2 in the wireless network cell. In addition, although the example shown only shows two frequency bands, it should be noted that for Mode 1 and Mode 2 services, the frequency bands may be further divided to define multiple channels. The sub-bands of the mode 1 and mode 2 allocated frequency bands are used by different users for simultaneous transmission.

The hopping of Mode 1 and Mode 2 in the OFDM frequency band is designed to help combat deep fading in the time domain and frequency domain, and to allow further adaptive channel resource allocation for Mode 1 and Mode 2 based on traffic load and overall channel conditions.

In addition, the hopping mode 1 and mode 2 division reduces the need for the same mode 1 and mode 2 division for a long time on the wireless network and in a single cell. Therefore, the mode 1 or mode 2 transmission may be the main transmission in different areas of the wireless network as determined by the UE service allocation (that is, more bandwidth is allocated). In fact, one or both of the two OFDMA modes, Mode 1 and Mode 2, may not exist in all areas of the wireless network at a given moment. However, Mode 1 is best to always exist in the wireless network because it is easier to support the low-rate signaling channel used to maintain the wireless network operation.

For mode 1 and mode 2, within a given symbol duration, based on the operation mode of each specific UE in the period and the mapping mode of the period, the simultaneous (but not necessarily synchronized) transmissions of different UEs are mapped to two One of the frequency bands 51 and 53 or is mapped to these two frequency bands.

Once the frequency band and mode of operation have been assigned to a given user, many different methods can be used to actually map the data to the frequency band. In an embodiment of the present invention, the mapping mode defines a corresponding set of space-time coding sub-blocks (STC-SB) in the time-frequency dimension. STC-SB is the mapping of data to wireless channels with both time and frequency dimensions. That is, a single STC-SB spans multiple subcarriers and multiple symbol durations.

Figure 1 shows an example of a single STC-SB 80. The STC-SB includes a limited number (10 in the example shown) of continuous OFDM subcarriers in the frequency dimension and one or more OFDM symbol durations in the time dimension (2 in the example shown).

To support coherent detection, pilot symbols are included in STC-SB. For example, STC-SB80 has two pilot symbols 82 on each end of its frequency range to allow interpolation in frequencies on the bandwidth between pilot symbols. The remaining subcarriers are used for data. The maximum size of STC-SB is usually limited by the frequency coherence bandwidth. Interpolation in which the spacing between pilots exceeds the coherence bandwidth will not result in effective channel estimation. This allows the receiver to use simple channel estimation methods.

It should be noted that the frequency coherence bandwidth is generally smaller than the corresponding bandwidths of bands 51 and 53. Therefore, each frequency band 51 and 53 can advantageously be further divided so that multiple STC-SBs can be sent to each frequency band 51 and 53 at the same time without overlap in the frequency domain. Therefore, in some embodiments, the STC sub-block can be regarded as the smallest uplink transmission unit provided by OFDMA. STC-SB can also be used as a time-frequency hopping unit. Since there is no restriction that all STC-SBs sent at the same time belong to the same UE, OFDMA is easily suitable for multiple users to access. In the following discussion, it is assumed that the STC sub-block is the smallest uplink transmission unit for mode 1 and mode 2 operation. However, it should be understood that once the corresponding frequency band is defined, other data mapping methods of Mode 1 and Mode 2 can be used.

To support uplink transmit power measurement, in some embodiments, the pilot of each UE is generated from a coding sequence and the power is increased. The positions of the pilot symbols of the users in the small area are preferably offset from each other in the frequency direction or the time direction. Adopt this kind of pilot channel realization scheme, do not need the preamble.

The mapping is implemented in the frequency band 50 shown in FIG. 2 so that for mode 1 and mode 2 operations, the STC-SBs of different UEs in the same cell/sector do not overlap in time or frequency. This greatly reduces intra-cell interference. In addition, in some embodiments, an orthogonal mapping mode that also provides time-frequency diversity is adopted for each user. The hopping (mapping) mode that can be used for mode 1 or mode 2 transmission is further described in detail below with reference to the details of mode 1. It also describes an orthogonal hopping pattern that reduces intra-cell interference and inter-cell interference.

Cell-specific coverage code In some embodiments, before performing STC-SB mapping (hopping), the cell-specific coverage code is applied to the transmission of all UEs in a specific cell. If cell-specific spreading codes are used throughout the wireless network, the result is that each cell can use the same set of Walsh codes. As mentioned above, the orthogonal hopping (mapping) mode can also be used for this purpose, and will be discussed further below.

The advantage of the frequency domain extension is that the interference in the frequency domain is reduced, and it is easy to realize the optimal/suboptimal MAP (maximum posterior probability) receiver and/or multi-user detection in the frequency domain, thereby significantly improving performance.

The MIMO operation mode OFDMA can be utilized with different antenna configurations. The simplest embodiment is to use one antenna for each UE, and each base station has one antenna (by sector when divided into sectors). In another embodiment, a SIMO (single input, multiple output) scheme with a single transmitting antenna and multiple receiving antennas is adopted. In another embodiment, a MIMO (multiple input, multiple output) scheme with multiple transmitting antennas and multiple receiving antennas is adopted. In another embodiment, a MISO (multiple input, single output) configuration is used. In another embodiment, the antenna configurations used for mode 1 and mode 2 transmission are different. For example, to save power, the UE can apply SIMO to Mode 1 and MIMO to Mode 2.

To support dual-antenna MIMO transmission, an STC-SB should include at least two OFDM consecutive symbols in the time domain. More generally, for an NxN system, there should be at least N OFDM consecutive symbols in an STC-SB. The number of consecutive OFDM subcarriers in an STC-SB can be determined again by the frequency coherence bandwidth of the common wireless channel.

Transmission mode As mentioned above, uplink transmission is divided into two modes. Mode 1 supports the provision of user dedicated channels with a fixed data rate to support real-time services, uplink signaling, and simple messaging. Mode 2 supports high-rate data burst transmission. The division of time and frequency resources between these two modes is best based on the traffic load balancing between these two modes in the radio network.

Mode 1 Description As described above, Mode 1 operation occurs in one frequency band of the entire OFDM frequency band. The following discussion relates to the operation of the Mode 1 frequency band when it is allocated at a given instant. As mentioned above, this frequency band can be statically or dynamically allocated to have a fixed or variable size.

Mode 1 according to the embodiment of the present invention is designed to support several simultaneous transmission (parallel) transmission channels per user. Depending on bandwidth requirements, each active UE can be allocated one or more of these concurrent transmission channels. These transmission channels can have corresponding data rates to support real-time services (such as voice), uplink signaling, and simple messaging. In some embodiments, the corresponding data rate is maintained through the use of power control and adaptive modulation.

More specifically, Mode 1 operates in an open or closed power control loop to provide parallel transmission channels carrying fixed-rate circuit data, low-delay circuit data, or high-rate packet data per UE.

On a per UE basis, the Mode 1 signal includes one or more orthogonal spreading codes used to separate transmission channels belonging to a single UE. Therefore, the modulation technique used for Mode 1 can be referred to as "multi-code (MC)-OFDMA". Since a single UE can synchronously send the code to divide the transmission channel, the orthogonality of the code division transmission channel is guaranteed through the wireless channel.

Multi-code OFDMA (MC-OFDMA) introduces code multiplexing on the "frequency and time division" formed by OFDMA.

Multiple parallel transmission channels can be signaling channels required for network maintenance, or they can be voice channels that require real-time services. Examples of different signaling channels that can be included in the uplink are further provided below.

FIG. 3 shows a schematic diagram of a transmission signal chain 200 that can be used to generate a mode 1 uplink signal of a single UE. It should be understood that the transmission signal chain 200 may be implemented by a combination of hardware, software, and corresponding firmware.

The transmission signal chain 200 includes a plurality of parallel transmission channels TC1100, TC2102,..., TCN110. The number of channels is determined by system design and bandwidth considerations. Users who want to operate in mode 1 need at least one such transmission channel. Each transmission channel TC1100, TC2102,..., TCN110 is connected in series to the corresponding orthogonal code spreading function 120, 122,...,130. The output of each extension function 120, 122, ..., 130 is coupled to an adder 35, which adds together the thus extended sequence. The output of the adder 35 is coupled to a pilot and space-time (ST) encoder 30, which provides two parallel outputs to hop pattern generators (HPG) 31 and 32, respectively. The hopping pattern is the same for both antennas. HPGs 31 and 32 are coupled to IFFT (Inverse Fast Fourier Transform) functions 33, 34 with outputs connected to corresponding antennas 21 and 22, respectively. The non-jumping embodiment will ignore HPG 31, 32.

In operation, each transmission channel 100, 102, ..., 110 transmits the modulated data symbol to the corresponding orthogonal code spreading function 120, 122, ..., 130 one at a time. For example, as shown at a given instant in FIG. 3, the transmission channels 100, 102, ..., 110 are displayed as providing the corresponding symbols S1, S2, ..., SN to the corresponding orthogonal code spreading functions 120, 122, ..., 130. The modulation technique used to modulate each modulated data symbol may be, for example, QAM (Quadrature Amplitude Modulation), 16 QAM, or 64 QAM. In addition, the transmission channel does not need to use the same symbol modulation technique.

Each orthogonal spreading function 120, 122, ..., 130 multiplies each symbol received from the transmission channel by a plurality of chips of the corresponding orthogonal code. In the preferred embodiment, the orthogonal code is a Walsh code of length L=16, so that each transmission channel generates 16 chips after spreading. It should be understood that other sizes of Walsh chips and other types of orthogonal codes can be used.

The corresponding chips of each orthogonal code spreader are added together by the adder 35. The output of the adder 35 is a sequence of L chips, each of which contains information for each transmission channel. The output of the adder 35 is sent to the pilot and ST encoder 30. For embodiments using multiple transmit antennas, the pilot and ST encoder 30 have two functions. First, for a dual-antenna system (or N-antenna system), it processes the chip sequence to generate two (N) chip sequences in order to transmit one sequence on each antenna within two (N) symbol durations. In one embodiment, this process is STBC. It should be understood that other mechanisms can be used to generate two (N) sequences. For example, see SMAlamouti's "Simple Transmit Diversity Technique for Wireless Communications" (SMAlamouti, "Simple Transmit Diversity Technique for Wireless Communications", IEEE J. Select. Area Commun., vol. 16, no. 8, pp. 1451-1458, Oct. 1998, and V. Tarokh, H. Jafarkhani, and ARCalderbank,") and V.Tarokh, H.Jafarkhani and ARcalderbanks "Orthogonal Design Space-Time Block Codes" (V.Tarokh, H.Jafarkhani, and ARCalderbank, "Space-time Block Codes from Orthogonal Designs", IEEE Trans. inform. Theory, July 1999). For example, a 16-chip signal can be processed by a space-time encoder to generate two 8×2 STC sub-blocks, one sub-block for each antenna. Other functions are generated from L composite chips UE-specific pilot signals are generated and added on either end of the STC-SB. This results in a 10x2 block for each antenna, which is generally represented by mark 16 with pilot signal 140 and STC symbol 142. For each antenna , This will be passed to the corresponding HPG 31, 32. HPG 31, 32 determines which sub-band of the mode 1 FFT bandwidth should be used for a specific transmission, and then the IFFT functions 33, 34 perform frequency-to-time conversion.

At any given instant, HPG 31 and 31 map the STC-SB they receive to the mode 1 OFDM frequency band subband currently used for mode 1 transmission. For Mode 1 transmission, the hopping pattern is unique to a single UE in a cell/sector, and can be pseudo-random. The mapping of each user is preferably extended to the time-frequency dimension by using the pseudo-hopping pattern to achieve time-frequency diversity. The transition unit is preferably an STC sub-block. The hopping mode will be discussed in more detail below.

Provides MC-OFDMA user mapping design optimized for high-speed mobility and mobile deployment. The sub-band mapping is determined by the channel propagation characteristics.

Figure 4 illustrates the transmission of user mode 1 signals in time and frequency by way of example. Similarly, the horizontal axis represents frequency and the vertical axis represents time. In this example, the Mode 1 frequency band is divided into three sub-bands, and the size of each of the three sub-bands is determined to carry the STC sub-block in the form of the sub-block 16 shown in FIG. 3. In this example, the Mode 1 frequency band also includes SACH subcarriers 131 and 133. These will be described further below. It can be seen that within the duration of each symbol, the user transmits on one of the three sub-bands, and the sub-band used hops nearby. Therefore, within the indicated symbol duration t1,...,t9, the user sends STC sub-blocks on each sub-band 130, 134, 132, 130, 135, 132, 130, 134, 132 in sequence.

Each sub-band defines a channel for mode 1 transmission. Preferably, no two users in a sector are allocated the same channel at the same time. Therefore, in the example of FIG. 4, the mode 1 transmissions of other users are sent at the time and frequency positions that are not occupied by the user mode 1 transmission. In this way, users in the cell are separated in frequency. In another embodiment, if very good synchronization can be achieved between users, as long as the users use different orthogonal spreading codes, they can be allocated overlapping frequency bands.

This MC-OFDMA-based Mode 1 uplink can support low-latency fixed data rate circuit data such as voice, simple messaging and signaling, and high-speed packet data services. In the simulation, it is found that the spectrum efficiency of MC-OFDMA is 5-10 times higher than that of 3G wireless systems using CDMA. In addition, it is also found that the simulation of MC-OFDMA improves the system capacity and the uplink data rate, both of which are orders of magnitude greater than that of the 3G wireless system using CDMA. These results do not mean that every implementation is equally effective.

The transmission channel of Figure 3 preferably includes channel coding (not shown). The range of the channel coding block preferably includes several hops of a user to achieve diversity gain and inter-cell interference averaging.

Fig. 5 is another example of possible occupancy patterns of the Mode 1 frequency band. This example shows time on the vertical axis and STC sub-blocks on the horizontal axis. The STC sub-block allocated to user 1 is summarized as 182, the STC sub-block allocated to user 21 is summarized as 183, and the STC sub-block allocated to user 3 is summarized as 184. In this case, the same transmission rate R is provided for the three users, and therefore, the same number of sub-blocks are allocated to each of the three users. It should be noted that the synchronous quadratic congruence code (synchronous quadratic congruence code) discussed below is used to generate a specific hopping pattern.

In the MC-OFDMA system, code division is used to transmit data of a single UE in parallel on the same STC sub-block. Since each STC sub-block is only allocated to one user in the sector, there is no inter-user interference in each STC sub-block. However, due to the loss of orthogonality caused by the fading channel, there is intra-user self-interference (inter-symbol interference). interference). MC-OFDMA can appropriately use the orthogonal spreading codes in the uplink to reduce self-interference. Due to the precise synchronization characteristics of the orthogonal codes, the MC-OFDMA system also allows low-complexity channel estimation and simple linear multi-code channels Detection, this is because all Walsh code channels are sent through the same propagation channel.

The spreading factor on each transmission channel of the adaptive SF MC-OFDMA can be variable and is best set according to the traffic load and channel conditions. After expansion, one symbol is represented by K symbols. This number K is defined as the "spreading factor". Note that K symbols will occupy K subcarriers in the OFDM system. The change of the spreading factor is realized by changing the mapping of the STC sub-block unit covered by the spreading code.

Therefore, in some embodiments, depending on the channel conditions and traffic load of a specific UE, the spreading factor is controlled by the scheduler of the base station. The base station can allocate more than one Walsh channel to circuit data channels that require higher protection or higher data rates. For Mode 1, the signal is power controlled, that is, the data load that each Walsh channel can carry is fixed. Therefore, the more Walsh channels allocated to a particular user, the higher the data rate. In addition, the use of a lower code rate for a given user will result in better protection.

Two other examples of how Mode 1 bandwidth may be allocated will now be described with reference to FIGS. 6A and 6B. Figure 6A shows how hopping can be performed in a system with two users, where the first user, user 1 is assigned a rate R, and the second user, user 2 is assigned a rate 2R. This means that the STC sub-block allocated to the second user needs to be twice the STC sub-block allocated to the first user. The sub-block allocated to user 1 is indicated as 180 in general, and the sub-block allocated to user 2 is indicated as 181 in general. It can be seen that the sub-block allocated to user 2 is twice the sub-block allocated to user 1.

In another example shown in Figure 6B, there are 4 users, among them, user 1 is assigned a rate R, user 2 is assigned a rate R, user 3 is assigned a rate R/2, and user 4 is assigned a rate R/2. The sub-block allocated to user 1 is summarized as 185, the sub-block allocated to user 2 is summarized as 186, the sub-block allocated to user 3 is summarized as 187, and the sub-block allocated to user 4 is summarized as 188. It can be seen that the blocks allocated for users 1 and 2 are twice the blocks allocated for users 3 and 4. Each STC transmission period includes one sub-block for each user 1 and 2, and only each second STC transmission period includes one sub-block for each user 3 and 4.

The power-controlled MC-OFDMA mode 1 operation is used for the transmission of slow traffic channels. As detailed below, in some embodiments, the same frequency band is used for RACH. In some embodiments, the slow traffic channel adopts the open-loop power control MC-OFDMA technology. An example power control solution is given below through the description of RACH.

System Access Channel (SACH) In some embodiments, the system access channel can be used as a fast uplink paging channel to signal the base station and the MAC status transition on the UE to the base station. The UEs that access the system, that is, the UEs in the power-on state or the standby state, do not transmit in mode 1 or mode 2. SACH signaling preferably has two states, namely active state and inactive state. SACH signals are periodically sent from all inactive UEs so that the base station can track UE timing and maintain synchronization during UE inactive mode.

In one embodiment, the SACH of a given user is two or more subcarriers allocated during certain periodic OFDM symbol periods. One of the subcarriers is preferably coded as a pilot channel, and the remaining subcarriers contain a differentially coded access request including at least one state indicating that the user is requesting the mode 1 and/or mode 2 capacity to be scheduled. SACH channels are allocated only to users in the standby state. Once the user enters the active state, the SACH allocation is cancelled and can be allocated to another user. The base station monitors all SACH channels, performs scheduling accordingly, and can maintain timing and synchronization during standby.

In the example of FIG. 4, two SACH channels 131, 133 are shown. Each SACH131, 133 occupies a pair of adjacent subcarriers in every fourth OFDM symbol period. The subcarriers allocated for the SACH channel can be along the frequency direction as shown in FIG. 4 or in the time direction.

It is best to allocate SACH subcarriers as shown in the example shown in Figure 4 so that they do not overlap with any user's mode 1 transmission in the cell. Once multiple SACH channels are defined, these subcarriers can be allocated to UEs in the cell using, for example, a paging channel. If there is no active downlink service of the UE for a certain period of time, and no uplink transmission request of the UE, the base station usually closes the dedicated uplink channel of the UE and allocates the SACH channel to it at the same time. Subsequently, the UE transfers from the active state to the standby state according to the signaling received from the base station. Subsequently, if the UE wants to start uplink transmission, it uses its dedicated SACH to notify the base station. Finally, if the UE does not respond within a certain period of time, the base station will notify the UE to transition from the standby state to the idle state. Once the user is idle, the user needs to use the following RACH to access the uplink system again.

The uplink signaling channel preferably provides a set of parallel low-latency circuit data signaling channels in Mode 1 transmission to support network operations. The definitions of these signaling channels are as follows: 1) DL channel condition (CQI/CLI) feedback-short block-coded downlink channel quality indicator and MIMO channel indicator for base stations to perform multi-user scheduling and adaptation Coding modulation and MIMO mode adaptation. It is best to define two data rates for this channel, a high data rate is used for fast adaptation, and a low data rate is used for slow adaptation.

2) DL ACK/NAK signaling-extended signaling used to indicate the confirmation of the success/failure of downlink packet reception.

3) Uplink buffer status (buffer full)-a short block coding indicator related to the UE uplink data buffering condition to allow the base station to schedule uplink mode 2 data bursts. Additional details about Mode 2 are provided below.

4) Uplink transmit power range-a short block code indicator related to the UE uplink transmit power head room (transmit power head room) to allow the base station to schedule uplink mode 2 data bursts.

5) Uplink rate indicator-a short block coding indicator related to the data channel rate indicator of the mode 1 and mode 2 traffic, used for demodulation and decoding by the base station receiver. For Mode 1, the rate indication can be used to support UE autonomous scheduling. For Mode 2, this channel can also be used to indicate the UE MAC identity.

Uplink traffic channels are as described above, and two types of uplink traffic channels are defined as follows: Fixed data rate dedicated traffic channel (mode 1) This mode 1 type of channel is designed for user dedicated channels with a fixed data rate , In order to support real-time services, usually voice services. The channel can be power controlled, preferably open-loop power control is used to support basic operations, and closed-loop power control is optionally applied.

In multiple uplink users, the non-overlapping allocation of STC sub-blocks can avoid intra-cell interference. It is best to design an orthogonal hopping mode so that it can be distributed to different users. For example, the synchronous quadratic congruence code yk=QCS(a,α,β,k,p) can be used as follows: ykQCS=[a(α+k)2+β]modp]]>k=0,. .p-1a=1, .., p-1α, β=0, .., p-1

This hopping mode can be used for user control in a cell. For inter-cell users, the following asynchronous quadratic congruence codes can be used to control inter-cell user hopping: ykQCA=[ak2+bk+c]modp]]> This irregular time-frequency unit allocation in OFDM symbols helps Reduce PAPR (peak-to-average power ratio).

For mode 1 transmission, it is best to arrange a random hopping mode so that in each STC block, only one/multiple STC sub-blocks are allowed to be sent for each user. In this case, for each user, only a small part of the sub-band corresponding to each OFDM symbol is sent, which allows the use of several PAPR reduction techniques, such as the H-infinitybased tone injection method or Constellation shaping methods, etc., to increase UE transmit power efficiency.

The hopping pattern in Figure 6 is generated using this method.

The power control of the uplink power control mode 1 traffic channel can adopt open-loop power control. In one embodiment, power control is implemented as follows: 1. The UE transmits RACH at a power that is inversely proportional to the long-term estimated DL C/I measurement value and the RACH characteristic spreading factor (detailed below) (more generally, The RACH power will be increased when the estimated value is decreased); 2. The base station measures the RACH power of the UE and sends back a power control command to the UE to increase/maintain/decrease the transmit power-in the absence of confirmation, this power control transmission is still visible To confirm, the power of another access attempt is increased; 3. The UE uses the power control command adjustment in the dedicated slow traffic channel to start the uplink transmission based on the power of the RACH power; 4. The base station controls the frame error rate based on the specific UE Uplink power.

The above detailed description assumes that sub-blocks are used to separate multiple users in mode 1, and it is best performed by sub-block hopping. In another embodiment of the present invention, if the synchronization between different users in a cell can achieve sufficient accuracy, multiple users can use code division to share OFDM subcarriers. An example of this is shown in Figure 7. In the figure, the signals used for UE-1 300, UE-2 302, UE-3 304..., UE-M 310 are shown as being spread by corresponding orthogonal codes. The orthogonal codes are Walsh codes in the example shown, namely Walsh-1320, Walsh-2 322, Walsh-3 324,..., Walsh-M 326. The figure shows a summer, which is used to illustrate that these signals will be added on the air interface and additively combined on the receiver. In this embodiment, all Mode 1 bandwidth can be shared by all users at the same time, or multiple sub-channels can be defined as in the previous embodiment, but each sub-channel is occupied by multiple users. Through this embodiment, it is easy to understand how to change the bandwidth allocated to each user by providing more or less Walsh codes for each user.

In another embodiment, in a slow fading environment, or in the case of nomadic deployment, MC-CDMA in the time direction is a feasible solution. In this arrangement, the pilot can be inserted cyclically by each user, and the pilot interval is sufficient to perform accurate channel estimation. In this case, a truly synchronized CDMA uplink can be achieved and inter-user interference can be completely eliminated. Figure 8 shows an example of this, which shows the same user and Walsh code extensions as in Figure 7. However, in this case, transmission is performed on adjacent subcarriers of a series of consecutive OFDM symbols. Therefore, the expansion is completed in the time dimension, rather than in the frequency dimension as in the case of Figure 7.

Therefore, during the RACH transmission, the BTS generates power control commands according to the RACH, and applies these commands to them at the beginning of the mode 1 service transmission. Subsequently, during the active mode 1 transmission, the power control command is directly generated by the mode 1 transmission, for example, based on the FER, and applied to the mode 1 transmission.

Random Access Channel (RACH) Another embodiment of the present invention provides a random access channel (RACH) for new UEs in a specific wireless network to access the system. It should be understood that other access schemes other than RACH and/or SACH may be adopted. When a UE is just powered on or has moved from another wireless network domain to an area covered by a specific wireless network, it can be regarded as a new UE of the specific wireless network. In either case, a new UE in a specific wireless network must be able to access the wireless network through the base station.

Referring to FIG. 9, this embodiment of the present invention provides RACH overlapping on the entire public wireless channel 50 or only on one of the two frequency bands 51 and 53 shown in FIG. 1. "Overlap" means that the RACH is transmitted simultaneously with other mode 1 signal transmissions of other users in time and frequency. RACH is therefore a form of interference to other users.

RACH is best implemented using a long spreading code, which is then mapped to the OFDM symbols in the defined RACH slot. The RACH slot is defined as a group of OFDM symbol widths that are best continuous in time. In the example of FIG. 9, each RACH slot includes 4 OFDM symbol widths, and 4 RACH slots, namely RACH slot 1, RACH slot 2, RACH slot 3, and RACH slot 4 are also displayed.

The RACH channel structure is preferably based on PN extension and superimposed on MC-OFDMA. For each RACH slot, multiple quasi-orthogonal PN codes define a set of RACH characteristics. This allows a set of parallel orthogonal ALOHA channels to be defined in each time slot. Since non-coherent detection and UE peak power limitation are used for the RACH channel to support a larger coverage area, the spreading factor is preferably very large, for example, between 210 and 214. Due to this processing gain, the power of the RACH feature can be transmitted at a very low relative power level: for example, -16dB, which constitutes very low interference to the service and signaling channels.

In some embodiments, the access UE transmits on the RACH channel as described above. In addition, it is better to apply the power ramp process, and therefore transmit the RACH channel with the lowest power, in order to reduce the inter-channel interference to the mode 1 service and signaling channel. More specifically, use very low power for the first attempt. There is no power control command from the base station as a failed attempt, and the next attempt will be made with a slightly increased power.

RACH channels are mapped to resources: a) Parallel ALOHA channels with specific RACH characteristics; b) Time-frequency dimension RACH time slots, which are different from STC sub-block units.

The number of allowed parallel ALOHA channels can be dynamically configured by the network based on traffic load conditions or the number of active users. The access UE randomly selects the RACH feature based on the slotted ALOHA protocol. The RACH feature can also be reused by non-neighboring base stations.

The RACH channel structure in this example is composed of RACH time slots, each RACH time slot includes 4 OFDM symbols, and there are 15 RACH time slots in a 10 ms frame. For each RACH slot, there are 16 RACH features that can be used to construct 16 concurrent RACH access attempts in one RACH slot. In some embodiments, as shown in FIG. 9, the mapping of RACH features to OFDM subcarriers is performed based on the Peano-Hilbert plane filling curve, so as to obtain better time-frequency diversity for RACH features. The Golay sequence can be used as a RACH feature to obtain a lower peak-to-average power ratio (PAPR).

In order to provide reliable and flexible random access channels for multiple users, RACH should preferably overlap in the mode 1 transmission bandwidth. A dedicated long complex PN/Golay code set is reserved for the RACH of each base station. The base station can determine the effective RACHPN/Golay code length according to all uplink services, or can define this length statically. The base station can broadcast this information through the DL signaling channel.

Figure 10A shows an example multiplexing scheme for generating RACHT and Mode 1 traffic channels. The figure shows the RACH channel 200 extended by Walsh-0 210 and covered by the first long code PN-0 using the multiplier 220. The figure also shows the mode 1 channel voice 202, CQI 204, ACK/NAK and data 208 extended by Walsh-1, Walsh-2, Walsh-3 and Walsh-M respectively (additional and/or different channels can be used) . The mode 1 channels are combined by the adder 221 and covered by the long code PN-1 by the multiplier 222. The adder 224 combines the RACH and Mode 1 signals. If RACH is only used for access, RACH and mode 1 signaling will be mutually exclusive.

The PN coverage of the Mode 1 traffic channel for a UE may be a component of the long PN coverage code. The coverage PN code of each base station is different from the coverage PN code of neighboring base stations. Therefore, the interference of these base stations can be averaged and whitened. Since the RACH PN code is much longer than the spreading code used for MC-OFDMA, the transmission power of the RACH can be much lower than the transmission power of the slow traffic channel. RACH should be transmitted with the lowest possible power to reduce its impact on slow traffic channels.

For example, RACH channel detection can be performed on the base station based on a continuous interference cancellation method. Other methods can also be used.

In some embodiments, RACH is also used for initial timing and synchronization. After randomly selecting a RACH feature, the access UE uses all available access frequency bands to transmit, which preferably includes all Mode 1 subcarriers. The base station searches for these access attempts, while performing timing and synchronization to determine the timing offset of the UE, thereby telling the user when its OFDM symbol transmission should start, so that all UE transmissions will share more or less common OFDM symbols on the base station boundary. Due to the different distance from the base station, the offset may be different.

The flowchart of Figure 11 summarizes the detailed method of joint RACH detection. The steps are as follows: Step 11-1: Transform the input data from the time domain to the frequency domain through the FFT with separate FFT window 1 and FFT window 2; Step 11-2: Restore the mode 1 service bits after decoding; Step 11- 3: Re-encode, re-interleave and re-map the recovered bits; Step 11-4: Re-spread through Walsh codes to regenerate Mode 1 service; Step 11-5: Add Mode 1 channel fading to obtain fading Mode 1 service ( Additional phase adjustment is required when window 2 is used); Step 11-6: Mode 1 service interference cancellation (subtract the recovered fading mode 1 service from all received signals in the frequency domain); Step 11-7: Extract reception after interference cancellation Step 11-8: Correlate the received RACH YRACH with all RACH characteristics and find the maximum value; Step 11-9: Get a new YRACH by multiplying YRACH with the corresponding phase vector, so that the FFT window is synchronized Shift within the search window; Step 11-10: Correlate the new RACH YRACH with all RACH features and find the maximum value; Step 11-11: Find the final maximum value among all local maximum values in the synchronization search window; The output of this process is the RACH feature index and synchronization position (RACH feature and FFT window position corresponding to the final maximum value).

The establishment of uplink transmission The following steps describe the procedure for the UE to initiate a connection with the access network: 1) After power-on, the UE synchronizes with the base station to obtain timing and frequency information, and at the same time selects the serving base station, for example, by detecting the downlink front Encoding.

2) The UE monitors the DL signaling channel to obtain information identifying the RACH PN code to be used in the cell/sector.

3) The UE measures the DL long-term C/I.

4) The UE sends the RACH code randomly selected from the code set of the serving base station via the ALOHA RACH channel. The transmit power is determined to be inversely proportional to the DL long-term C/I measurement value.

5) If the base station successfully detects the RACH code, it will measure the time offset of the UE, and then send the initial dedicated uplink access channel grant and RACH code index and time offset information. The UE then detects this feature to identify the access permission through the DL signaling channel.

6) The UE adjusts its timing. If it wants to start uplink data transmission, it sends back its ID, its CQI report information, and uplink traffic load request, for example, via the initial dedicated uplink signaling channel, as described above A parallel low-latency circuit data channel loopback.

7) The base station schedules uplink multi-user access based on the uplink channel conditions measured from the mode 1 pilot and the service requirements reported by different active UEs.

8) The channel resource allocation and coding/modulation primitives of different UEs are sent via the DL signaling channel.

Every time the UE needs a new uplink connection, it sends a new access request through the access SACH. In order to improve the spectrum efficiency, the UE can adopt the MC-OFDMA scheme to buffer some short messages within the delay tolerance, and then send these messages on its dedicated slow traffic channel. Alternatively, each time the UE requests a new connection and transitions to the active state, the UE may use the common uplink channel of the TDM operation mode to send a signal to the base station to indicate that the state transition is performed.

Fig. 10B is a block diagram of another transmitter embodiment similar to the transmitter shown in Fig. 10A, but in which coding is performed on sub-blocks. In this example, there are N transmission channels 500, 502 (only two are shown), and each channel is connected to a corresponding TURBO encoder 504, 506 that performs channel coding. The coded output is fed to an interleaver block 508, from which a parallel group of interleaved outputs is generated, these parallel interleaved outputs are fed to a modulator 510, which preferably performs QAM mapping. The output of the QAM mapping modulator 50 is a set of modulation symbol streams. These symbol streams are all input to a demultiplexer 512, which routes the modulated symbols to one of M Walsh sequence spreading function blocks 514, 516 (only two are shown). N and M are not necessarily equal. The data sequence is multiplied by the chip sequence of the corresponding Walsh sequence through adders (equivalent to multipliers) 518 and 520, and each Walsh sequence spreader expands the corresponding output of the multiplexer 512. The content of the transmission channel is added together by the adder 522, and the first long code coverage is applied at 524. The RACH channel is denoted by 530. It uses Walsh-0 sequence for Walsh spread spectrum. More generally, any Walsh sequence different from those used by other channels can be used. However, when the Walsh-0 sequence is effectively used, Walsh spreading is not used, and the RACH channel content is directly sent to the multiplier 530, in which the second PM cover code is applied. The RACH channel content and the remaining content are combined in the adder 532. The remaining elements of Fig. 10B are the same as those described in Fig. 3, and are not repeated here. It should be noted that although the figure shows that the adder 532 has two inputs, for a single UE, usually only one input is valid at a given instant. While using RACH, the user is in an inactive state and therefore does not transmit on the data channel. Similarly, users do not need RACH when sending data. In this embodiment, it can be seen that multiple transmission channels 500 and 502 are spread with Walsh code sequences 514 and 516 after their content is encoded and then interleaved. Using the appropriate block size selected in the encoders 504 and 506, the appropriately coded block is extended to a plurality of sub-blocks, and these sub-blocks hop according to the hopping mode 32.

Description of Mode 2 In another embodiment of the present invention, Mode 2, which is preferably operated in conjunction with Mode 1, adopts centralized scheduled transmission to provide high-speed data bursts with controlled rates. It is best to use the maximum power in order to transmit at the highest possible rate in mode 2 to maximize throughput. Mode 2 supports time division multiplexing (TDM) multi-user services. It is best to adopt adaptive coding and modulation techniques to support high-rate data bursts.

Rate-controlled FDM/TDM-OFDMA is used for multi-user high-rate data burst transmission. According to the channel quality QoS and traffic load of each UE, the base station scheduler schedules the access of multiple users, including the channel resource allocation and coding/modulation scheme of each UE. A group of STC sub-blocks can be allocated to each UE. To obtain time/frequency diversity, the STC sub-block of each UE can hop on the frequency-time plane according to a certain pattern. Figure 12 shows an example of the STC sub-block allocation scheme among three UEs. However, if the frequency synchronization requirements between different UEs are to be reduced, the STC sub-blocks allocated to a specific UE should be combined to reduce the inter-user interference between the STC sub-blocks of different UEs. The allocated STC sub-block can be regarded as a dedicated fast traffic channel.

In the example shown, a frequency band is allocated for mode 2 operation, and the frequency band is wide enough for three STC sub-blocks. These sub-blocks can be allocated for mode 2 operation in any way. However, it is better to allocate these blocks in a continuous manner both in time and frequency. Therefore, in the example shown, the first block 84 is shown, which includes 2 adjacent STC sub-blocks in frequency, and is transmitted for 4 STC sub-blocks in time. The first block 84 is used for user 1 pilot sub-carrier 93 and user 1 data sub-carrier 94. Likewise, block 86 for user 2 pilot 95 and data 96 is shown. In this case, the block 86 includes a single STC sub-block, which is transmitted corresponding to 5 consecutive STC sub-blocks on the frequency. Mark 89 indicates a block composed of the allocated sub-blocks of user 3, and has user 3 pilot sub-carrier 97 and data sub-carrier 98. The other STC sub-block combinations are indicated as 90 and 92.

Of course, it should be understood that the bandwidth allocated for mode 2 operation is arbitrary, and different numbers of STC sub-blocks can be adapted to the thus defined frequency band. The size of the STC sub-block is of course variable, but this is best limited by the frequency coherence bandwidth.

Figure 13 is a functional block diagram of a transmitter for mode operation. This example architecture includes a MAC interface 500 through which packets to be sent in mode 2 can be received. The packet is then processed by a data scrambler 502, a CRC addition block 504, a TURBO encoder 506, a rate matching block 508, a bit interleaver 510, a QAM map 512, and a symbol interleaver 514. The output of the symbol interleaver 514 is fed to A- The STC function block 516 generates an output from which this output is then multiplexed with the mode 1 data as shown at 518. Understand that this diagram is a very specific example, and usually these blocks may not be needed at all.

It should be noted that in the example allocation of STC sub-blocks for Mode 2 in Fig. 12, the STC sub-blocks of a given user are continuously allocated. In a preferred embodiment, the STC sub-blocks transmitted in Mode 2 also undergo frequency hopping. In this case, when a mode 2 transmission opportunity is allocated to users, the allocation needs to contain enough information to determine the hopping mode so that each user can accurately identify the time and frequency at which the STC sub-block will be used to send packets.

Figure 15B shows an example of how to combine Mode 1 and Mode 2 in the transmitter architecture. For example, the mode 1 output is generated on the transition mode output of FIG. 3 or FIG. 10B, which is generally represented by 550, and the mode 2 output generally represented by 552 is generated by the mode 2 transmission architecture of, for example, FIG. The multiplexer function block 554 to which the IFFT 556 is connected. This function will be implemented for each antenna. Figure 15B shows an example of how to perform multiplexing. Here, the mode 1 input to the multiplexer 554 is generally represented by 560, and the mode 2 input to the multiplexer 554 is generally represented by 562. After multiplexing, the input to the IFFT function block 556 generated by the MUX 554 is generally represented by 564.

Uplink rate control In order to achieve rate control, the scheduler needs C/I information of all active UEs. However, due to the variability of interference, it is difficult to measure the uplink C/I. In the coding/modulation selection for uplink mode 2 transmission, a new rate control loop can be applied. The flowchart of Figure 14 illustrates an example uplink rate control and implementation.

Step 14-1: The base station measures the signal strength of all active UEs based on the pilot received from the mode 1 transmission.

Step 14-2: The base station schedules the initial access of multiple UEs according to these initial measurement values.

Step 14-3: The base station sends transmission resource and parameter signals to the UE.

Step 14-4: The UE monitors the downlink signaling channel to obtain mode 2 transmission instructions, including the allocated STC sub-blocks and coding/modulation primitives, and then initiates mode 2 transmission.

Step 14-5: The base station detects the block error rate of the data received from the UE. If the block error rate is higher/lower than the target value, by changing the coding and modulation primitives, a command is sent to the UE to reduce/increase the transmission rate.

Step 14-6: The base station reschedules user mode 2 transmission.

Step 14-7: The UE adjusts its coding and modulation primitives according to the rate control command.

Step 14-8: The base station sends the new rate control command to the UE.

In another embodiment, the UE can measure the long-term power intensity at the serving base station and set the modulation by using multi-level progressive coding and modulation feedforward transmission. It is understood that other uplink rate control methods can be used. Alternatively, each user can be assigned a static rate for Mode 2 transmission.

Referring now to FIG. 1, a system diagram for the OFDMA system is shown. In the figure, 600 generally represents the OFDMA receiver, and 602 and 604 generally represent two OFDMA transmitters. The OFDMA receiver 600 is usually a base station, and the OFDMA transmitters 602, 604 are wireless terminals such as mobile stations. The terminology used for these devices is often implementation specific. The functions required by the network can be referred to as "wireless terminals". This will include base stations, Node Bs, repeaters, or any other system devices that want to provide this functionality. The figure also shows the downlink control channel 652 from the OFDMA receiver 600 to the first OFDMA transmitter 602 and the downlink control channel 650 from the OFDMA receiver 600 to the second OFDMA transmitter 604. The OFDMA receiver 600 is shown to include a RACH detection function 610, a mode 2 rate control function 612, a mode 1 power control function 614, and an OFDMA receiving function 616 responsible for receiving mode 1 and mode 2 data of multiple users. Each OFDMA transmitter 602, 604 has a corresponding mode 1 function 618, 630, a corresponding mode 2 function 620, 632, a corresponding RACH function 622, 634, and a corresponding SACH function 624, 636. It should be understood that in OFDAM receiver 600, many other functions are usually required in a complete system. In addition, the displayed functions can be implemented as separate physical blocks, or can be integrated into a single design implemented with software and/or hardware and/or firmware. This is also true for each OFDMA transmitter 602, 604. In addition, it should be understood that not all embodiments require all the functional blocks shown in FIG. 1. For example, in an embodiment that does not use RACH, RACH function blocks 622, 634, and 610 will not be used. Note that the detailed structure of the downlink control channels 650, 652 is not provided. It is understood that any applicable downlink channel can be used for this purpose.

The SACH allocation and monitoring function 617 is also displayed in the OFDMA receiver 600. Correspondingly, in OFDMA transmitters 602 and 604, corresponding SACH generators 624 and 636 are provided. Each OFDMA transmitter 602, 604 is also shown as having a corresponding control channel receiver 640, 642.

The content is only used to illustrate the application of the principles of the present invention. Those skilled in the art may adopt other arrangements and methods without departing from the spirit and scope of the present invention. Based on the above teachings, many modifications and changes of the present invention can be realized. Therefore, it is to be understood that within the scope of the appended claims, the present invention can be implemented in different ways than specifically described herein.