Random access dimensioning methods and procedures for frequency division multiplexing access systems

Method for random access dimension of frequency division multiple access system

The present disclosure relates to radio communication, and in particular, to methods and procedures for random access dimensioning in a frequency division multiple access system.

A radio (wireless) communication system can be composed of an access network and multiple access terminals. The access network may include an access point (such as node B, base station, or classifier), which allows access terminals to connect to the access network and use various types of channels for uplinking (UL: terminal to network) ) Communication and downlink (DL: network to terminal) communication. The access terminal can be a user equipment (UE), a mobile station, or the like.

Although the concepts described below can be applied to different types of communication systems, the Universal Mobile Telecommunications System (UMTS) will be described for exemplary purposes only. A typical UMTS has at least one core network (CN) connected to at least one UTRAN (UMTS Terrestrial Radio Access Network), and UTRAN has Node B as an access point for multiple UEs.

Figure 1 shows the radio interface protocol architecture based on the 3GPP radio access network standard. The radio interface protocol has a horizontal layer including a physical layer, a data link layer, and a network layer, and has a user plane (U plane) for transmitting user data and a user plane for transmitting control information. The vertical plane of the control plane (C plane). The user plane is an area that processes traffic information with users, such as voice or Internet Protocol (IP) packets. The control plane is an area that processes control information used to interface with a network, maintain and manage a call.

The protocol layer in Figure 1 can be divided into a first layer (L11), a second layer (L2), and a third layer (L3) according to the three lower layers of the Open System Interconnection (OSI) standard model. The first layer (L1; physical layer (PHY)) provides information transmission services to an upper layer by using various radio transmission technologies. The physical layer is connected to an upper layer called the media access control (MAC) layer via a transmission channel. The MAC layer and the physical layer exchange data via the transmission channel. The second layer (L2) includes a MAC layer, a radio link control (PLR) layer, a broadcast/multicast control (BMC) layer, and a packet data convergence protocol (PDCP) layer. The MAC layer processes the mapping between the logical channel and the transmission channel, and provides the allocation of MAC parameters for allocating and reallocating radio resources. The MAC layer is connected to an upper layer called the Radio Link Control (RLC) layer via a logical channel. Various logical channels are provided according to the type of information transmitted.

The MAC layer is connected to the physical layer through the transmission channel, and can be divided into a MAC-b sub-layer, a MAC-d sub-layer, a MAC-c/sh sub-layer, and a MAC-hs sub-layer according to the type of the managed transmission channel. Layer and a MAC-m sublayer. The MAC-b sub-layer manages BCH (broadcast channel), which is a transmission channel for processing the broadcast of system information. The MAC-c/sh sub-layer manages shared transmission channels, such as the forward access channel (FACH) or the downlink shared channel (DSCH) (which is shared by multiple terminals), or the random access channel in the uplink (RACH) ). The MAC-m sublayer can process MBMS data. The MAC-d sublayer manages a dedicated channel (DCH), which is a dedicated transmission channel for a specific terminal. The MAC-d sublayer is located in a serving RNC (SRNC), which manages a corresponding terminal, and a MAC-d sublayer also exists in each terminal.

Depending on the RLC mode of operation, the RLC layer supports reliable data transmission, and performs segmentation and sequential connection on a plurality of RLC service data units (SDUs) delivered from an upper layer. When the RLC layer receives the RLC SDU from the upper layer, the RLC layer adjusts the size of each RLC SDU in an appropriate manner based on the processing capacity, and then generates a data unit by adding header information to it. These data units (called Protocol Data Units (PDU)) are transferred to the MAC layer via logical channels. The RLC layer includes an RLC buffer for storing RLC SDUs and/or RLC PDUs.

The BMC layer schedules cell broadcast (CB) messages sent from the core network and broadcasts the CB messages to terminals located in a specific cell or multiple cells.

The PDCP layer is located on the RLC layer. The PDCP layer is used to efficiently transmit network protocol data (such as IPv4 or IPv6) on a radio interface with a relatively small bandwidth. For this purpose, the PDCP layer reduces unnecessary control information used in the wired network, that is, implements a function called header compression.

The Radio Resource Control (RRC) layer at the bottom of the third layer (L3) is only defined in the control plane. The RRC layer controls the transmission channel and physical channel related to the setting, reconfiguration and release or cancellation of the radio carrier (RB). RB designates a service provided by the second layer (L2) for data transmission between the terminal and UTRAN. Generally speaking, the setting of RB refers to the process of stipulating the characteristics of a protocol layer and a channel that need to provide a specific data service, and setting individual detailed parameters and operation methods. In addition, the RRC layer handles user mobility and additional services in the RAN, such as location services.

The E-UTRA (Evolved UMTS Terrestrial Radio Access) system, also known as the LTE (Long Term Evolution) system, is regarded as related to the PS (Packet Handover) domain with shared resources only to be used. In this new background with faster latency and higher capacity requirements, the use of LTE RACH (LTE Random Access Channel) should be somewhat different from the existing GSM and UMTS systems to meet the access requirements dedicated to LTE. E-UTRA and LTE are related to the principle of Orthogonal Frequency Division Multiplexing (OFDM).

OFDM is based on the known technique of Frequency Division Multiplexing (FDM). In FDM, different streams of information are mapped to separate parallel frequency channels. A frequency guard band separates each FDM channel from other channels other than itself to reduce interference between adjacent channels. This OFDM technology is different from traditional FDM in that multiple carriers (called subcarriers) carry the information stream, and these subcarriers are orthogonal to each other; (that is, the bandwidth of the independent subcarriers, It is smaller and arranged so that the maximum value of a carrier can correspond to the first minimum value of adjacent carriers) and a guard time can be added to each symbol to counteract the channel delay spread.

Figure 2 shows an exemplary frequency-time representation of an OFDM signal. As you can see, the signal can be composed of multiple sub-carriers, and each sub-carrier (with a specific bandwidth or frequency range) can carry data (or information), and the data (or information) is represented by a symbol with a guard interval in between. .

The multi-user system includes both up-chain and down-chain. In the uplink, the network measures the attenuation at the different uplink sub-carriers. Based on the measurement, the network disperses the sub-carriers, and the different UEs must use uplink transmission. In the downlink, the UE measures the attenuation of each downlink carrier. For a better UE reception process, the measurement result is sent to the network of the decentralized downlink carrier. In a random access protocol, a UE transmits a known signal sequence (that is, a designated code signature) to a base station (Node B). To this end, first, the UE listens to a pilot channel transmitted by the network, and after detection, the UE synchronizes the OFDM symbols transmitted by the network. Second, the UE listens to a random access sequence, a broadcast system information channel, and a number of subcarriers assigned to a random access channel (RACH), and then transmits a random access sequence in the random access channel . After transmitting a certain number of random access sequence cycles, the UE checks whether the network has granted the access.

A general overview of the W-CDMA random access procedure will now be considered.

The transport channel RACH and the two physical channels PRACH and AICH are all related to this procedure. The transport channels are the channels supplied from the physical layer to the protocol layer (MAC). There are several types of transmission channels to transmit data with different properties and transmission formats on the physical layer. The physical channel is identified in FDD mode by coding and frequency. These physical channels are usually based on the one-level configuration of the radio frame and slot. The form of the radio frame and slot depends on the symbol rate of the physical channel. The radio frame is the smallest unit in the decoding process and consists of 15 time slots. The time slot is the smallest unit in the 1-bit sequence of the layer. Therefore, the number of bits that can be accommodated in a time slot depends on the physical channel. The transport channel RACH (Random Access Channel) is an uplink common channel, which is used to transmit control information and user data. It is used in random access and is used for low-rate data transmission from the higher layer. The RACH is mapped to the physical uplink channel called PRACH (Physical Random Access Channel). The AICH (Acquisition Indication Channel) is a common channel in the next chain, and it exists as a pair together with the PRACH used for random access control.

The transmission of PRACH is based on a slotted ALOHA approach with a fast acquisition instruction. The UE randomly selects an access resource and transmits the RACH preamble part of a random access procedure to the network. The preamble is a short signal, which is sent before the transmission of the RACH connection request message. The UE repeatedly transmits the preamble by increasing the transmission power every time the preamble is sent, until the UE receives an AI (acquisition indication) on the AICH (acquisition indication channel), The AICH is instructed by the network to detect the preamble. Once it receives the AI, the UE stops the transmission of the preamble, and at that point sends the message part at the same power level as the transmission power of the preamble, plus One of the signals is offset. This random access procedure avoids a power ramping procedure for the overall message. This power ramp procedure will generate more interference due to the unsuccessful transmission of the message, and will be less efficient due to the larger delay, because it will be more inefficient before the message is successfully received and an acknowledgement can be given. More time will be spent on decoding the message.

The main feature of the RACH is that it is a contention-based channel, which means that due to simultaneous access by several users, collisions may occur, so that the initial access message cannot be decoded by the network. The UE can only start the random access transmission (both preamble and message) at the beginning of an access slot. This access method is therefore a type of time slot ALOHA approach with fast retrieval instructions.

Figure 3 shows an example of an access slot related to the transmission of a preamble, a message, and an extraction instruction (AI).

Figure 4 shows an example of the number of RACH access slots and their spacing.

Referring to Figures 3 and 4, the time axis of RACH and AICH is divided into time intervals, called access slots. Every two frames have 15 access slots (one frame length is 10 milliseconds or 38400 pieces), and they are separated by 1.33 milliseconds (5120 pieces).

Figure 5 shows an example of the reception of the AICH access slot via the UE's lower link and the transmission of the UE's uplink PRACH access slot. That is, Figure 5 shows the transmission timing relationship between PRACH and AICH.

Figure 6 shows a table with available uplink access slots for different RACH secondary channels.

Refer to Figures 5 and 6, which access slots can be used for random access transmission, and what timing offset information is used between RACH and AICH, between two consecutive preambles, and between the last preamble and messages, is based on Sent from the Internet. For example, if the AICH transmission timing is 0 or 1, it will send 3 or 4 access slots after the last preamble access slot transmission, respectively.

At the same time, referring to Figs. 5 and 6, the timing at which the UE can send the preamble is divided by random access sub-channels. A random access secondary channel is a subset, which includes the combination of all uplink access slots. There are 12 random access sub-channels in total. The random access secondary channel is composed of access slots.

Figure 7 shows an exemplary format of the pre-code signature. The preamble is a short signal, which is sent before the transmission of the RACH message. A preamble is composed of 4096 pieces, which is a sequence of 256 repeated Hadamard codes of length 16 and a scrambling code designated from the upper layer. Hadamard code refers to the signature of the pre-sequence code. There are 16 different signatures and a signature system (based on ASC from the available signature group) is randomly selected and repeated 256 times for each transmission of the preamble part.

Figure 8 shows an exemplary structure of a random access message part. The message part is expanded by the short code of the OVSF code uniquely defined by the pre-code signature, and the code is expanded to be used as the pre-code signer. The radio frame of the message part of 10 milliseconds is divided into 15 slots, each composed of 2560 pieces. Each slot is composed of a data part and a control part that transmits control information (boot bit and TFCI). The data part and the control part are conducted in parallel. The 20 millisecond long message part consists of two consecutive message part radio frames. The data part is composed of 10*2k bits (k=0, 1, 2, 3), which corresponds to the expansion factor (SF=256, 128, 64, 32).

Figure 9 shows an exemplary format (structure) of AICH. AICH consists of a repeating sequence of 15 consecutive access slots, each with a length of 40-bit intervals (5120 slices). Each access slot is composed of two parts, an acquisition instruction (AI) composed of 32 real-valued signals a0,...,a31, and a part of 1024 slices of the duration of the transmission closed.

When the network detects the transmission of the RACH preamble with a certain signature in a RACH access slot, it repeats the signature in the relevant AICH access slot. This means that the Hadamard code used as the signature on the RACH preamble is adjusted to the AI part of AICH. The extraction instructions corresponding to the signature can take values +1, -1, and 0, depending on whether a positive confirmation, a negative confirmation, or no confirmation is provided to a specific signature. The positive polarity of the signature indicates that the preamble has been retrieved and the message can be sent. Negative polarity indicates that the preamble has been captured and the power ramp process will be stopped, but the message should not be sent. When due to congestion in the network, this negative confirmation is used, and a transmitted message cannot be processed at present. In this case, the access attempt needs to be repeated later by the UE.

Regarding the random access procedure on the protocol layer (L2), the network is mainly based on the access class (AC) to which the UE belongs to determine whether the mobile station is allowed to use radio access resources. A designated priority level is implied by the access level stored on the UE SIM card.

After that, some features of access control will be described. It should be noted that the relevant standards related to this subject are 3GPP TS 22.011.

Regarding the purpose of access control, in some cases, it will be necessary to prevent UE users from making access attempts (including emergency call attempts) or responding to paging within a prescribed area of the PLMN (Public Land Mobile Network). These situations may occur during an emergency or during which 1 of 2 or more co-located PLMNs has failed. The broadcast message should be available on a cell-by-cell basis, which indicates the level of users restricted by the network access. The use of this facility allows network operators to prevent overloading of access channels under critical conditions. The access control is not expected to be used under normal operating conditions.

For allocation, all UEs are members of one of ten randomly allocated action ports, which are defined as access levels 0-9. The number of mobile ports can be stored in a SIM/USIM used for the UE. In addition, actions can be members of one or more of 5 special types (access levels 11 to 15), which can also be stored in SIM/USIM. These can be allocated to specific high-priority users as follows. (This list does not imply a priority order): Level 15-PLMN personnel; Level 14-Emergency services; Level 13-Public use (such as water/gas suppliers); Level 12-Security services; Level 11-For PLMN use.

For operation, if the UE is a member of at least one access level, it corresponds to the permitted level when sending through the air interface, and the access level can be applied in the service network, allowing access attempts. Otherwise, access attempts are not allowed.

The access levels can be applied as follows: Level 0~9-Local and visiting PLMN; Level 11 and 15-Local PLMN only; Level 12, 13, 14-Local PLMN and local visiting PLMN only.

Any number of these levels can be limited at any one time.

For emergency calls, an additional control bit known as access level 10 is also sent to the UE through the air interface. This indicates whether network access for emergency calls is allowed to be used for UEs with access levels 0 to 9 or without an IMSI. For UEs with access levels 11 to 15, if the access level 10 and related access levels (11 to 15) are restricted, emergency calls are not allowed. Otherwise, emergency calls may be allowed.

Hereinafter, the mapping of the access level (AC) will be described. It should be noted that the relevant standards related to this subject are 3GPP TS 25.331.

In UMTS, the access level is mapped to the access service level (ASC). Eight different priority levels have been defined (ASC0 to ASC 7), among which level 0 is the highest priority.

For the mapping from access level to access service level, the access level should only be applied during initial access, that is, when sending an RRC connection request (CONNECTION REQUEST) message. A mapping between the access class (AC) and the access service class (ASC) will be indicated by the information elements AC to ASC mapped in the system information block type 5. The correspondence between AC and ASC is indicated in Figure 10.

Figure 10 shows a table showing the correspondence between AC and ASC. The nth information element indicates an ASC number i in the range 0-7 to AC. If the ASC indicated by the nth information element is not defined, the behavior of the UE is not specified.

For random access, the parameters implied by the individual ASC should be used. In the case that the UE is a member of several ACs, it should select the ASC as the highest number of ACs. In connected mode, AC should not be applied.

An ASC is composed of a subset of the RACH preamble signature, the access slot allowed for this access attempt, and a sustained value corresponding to a probability Pv1 to attempt transmission. Another important mechanism for controlling random access transmission is the load control mechanism, which allows to reduce the load of incoming traffic when the collision probability is high or when the radio resource is low.

According to the interference coordination technology, this disclosure provides coordination of the sub-carrier frequency to the RACH communication link, so as to maximize the possibility of correct detection and minimize the error detection of random access sequences. As a result, the present disclosure provides a method for determining random access resources executed by a mobile terminal. The method includes the following steps: receiving information from a network on effective random access resources; The received information determines how to derive the allowed random access resources; measures the received signal quality of at least one of a cell being accessed and a neighboring cell; and based on the decision step And measurement steps to derive the allowed random access resources. Similarly, the present disclosure provides a method for determining random access resources executed by a network. The method includes at least the following steps: transmitting information to a terminal on an effective random access resource; and transmitting and following the link One of the radio signals measures at least one related parameter to allow the terminal to decide how to derive the random access resources that are being allowed.

One aspect of the present invention is a method for determining random access resources executed by a mobile terminal. The method includes at least the following steps: receiving information from a network on effective random access resources; according to preset values Or determine how to derive the allowed random access resources from the information received from the network; measure the received signal quality of at least one of a cell being accessed and a neighboring cell; and The allowed random access resources are derived based on the decision step and the measurement step.

Another aspect of the present invention is a method for determining random access resources executed by a network. The method includes at least the following steps: transmitting information to a terminal on an effective random access resource; and transmitting and One of the downlink radio signals measures at least one related parameter to allow the terminal to determine how to derive the random access resources that are being allowed.

One aspect of this disclosure is based on the inventor's cognition on the problems and shortcomings of the above-mentioned related technologies. Based on this recognition, the characteristics of this disclosure have been developed.

Although the following description will refer to the optimized RACH procedure of UMTS for explanatory purposes only, the features of this disclosure are obviously intended to be applied to various other types of communication methods and systems, which will benefit from using the specific features of this disclosure.

Figure 11 shows a flow chart of an exemplary control access procedure. It should be noted that the relevant standard on this subject is 3GPP TS 25.321.

The control access procedure can be implemented in the following five steps: (1) The existing specifications provide many RACH transmission control parameters, which are stored and updated by the UE based on the system information broadcast by the Internet. RACH transmission control parameters include entity RACH (PRACH), access service class (ASC), the maximum number of preamble tilt cycles Mmax, the range used for the timer shift interval TBO1, which is the transmission time interval of 10 milliseconds NBO1max and NBO1min is given, which can be applied when receiving a negative acknowledgement on AICH.

(2) The UE maps the designated AC to an ASC, and a count value M is set to zero.

(3) The count value M is incremented by 1. Secondly, the UE decides whether the count value M representing the number of transmission attempts exceeds the maximum number of RACH transmission attempts allowed Mmax. If so, the UE regards the transmission as unsuccessful.

(4) However, if M is less than or equal to the maximum number of allowed RACH transmission attempts Mmax, the UE updates the RACH transmission control parameters. In the next step, a 10-millisecond timer T2 is set. The UE decides whether to try transmission according to the persistence value Pi associated with the ASC selected by the UE. To be clear, a random number Ri is generated between 0 and 1. If the random number Ri is less than or equal to the continuous value Pi, the UE tries to transmit via a designated RACH resource. Otherwise, the UE waits for the 10-millisecond timer T2 to expire, and then performs the procedure in step (4).

(5) When an access attempt is transmitted, the UE determines whether the network responds with an acknowledgement (ACK) response, a non-acknowledgement (NACK) or no response. If no response is received from the network, after the timer T2 expires, the process is executed again from step (3). If a NACK is received (which indicates that it is often unsuccessfully received by the network due to collisions), the UE waits for the timer T2 to expire, and then generates a backshift value NBO1, which is associated with the maximum and minimum of the PRACH assigned to the UE The back shift value is randomly selected between NBO1max and NBO1min. Then, before performing the process from step (3), the UE waits for a shift interval TBO1 equal to 10 milliseconds multiplied by the back shift value NBO1. If an ACK is received (which indicates the reception of UE transmission via the network), the UE starts message transmission.

The random access procedure on the physical layer (L1) will be described below.

The physical random access procedure is initiated when a request comes from the MAC sublayer (L2).

Before the physical random access procedure can be initiated, layer 1 should receive the following information from the higher layer (RRC):-Preamble code mixing.

The length of the message, 10 or 20 milliseconds.

-AICH_Transmission_Timing parameter [0 or 1].

-Available signature group and available RACH sub-channel group for each access service class (ASC).

-Power Ramp Step[Integer>0].

-Parameter Preamble Retrans Max[integer>0].

-Initial preamble power Preamble_Initial_Power.

-Power offset Pp-m=Pmessage-control-Ppreamble, measured in decibels, which is between the power of the last transmitted preamble and the control part of the random access message.

-Transmission format parameter group. This includes the power offset between the data part and the control part of the random access message for each transmission format.

At each initial stage of the physical random access procedure, layer 1 should receive the following information from the higher layer (MAC):-The transmission format to be used for the PRACH message part.

-ASC for PRACH transmission.

-Data to be transmitted (transmission block group).

The physical random access procedure is implemented according to the following procedures (steps): 1. In the random access sub-channels that can be used for the relevant ASC, an access slot is from the access slot that can be used for the next full access slot group 2 random selection. If there is no available access slot, an access slot is randomly selected from the access slots available for the next full access slot group.

2. A signature is randomly selected from the group of available signatures in the given ASC.

3. The preamble retransmission counter is set at Retrans Max, which is the maximum number of preamble retransmission attempts.

4. The preamble transmission power is set at Preamble Initial Power, which is the initial transmission power of the preamble.

5. The preamble is transmitted based on the selected uplink access slot, signature and set transmission power.

6. If no ACK or NACK corresponding to the selected signature is detected in the chain access slot corresponding to the selected upper chain access slot.

-The next available access slot is selected from the random access sub-channels in the given ASC.

-A new signature is randomly selected from the available signatures in the given ASC.

-The transmission power of the preamble is increased by the Power Ramp Step, which is the width of the power ramp step.

-The preamble retransmission counter is decreased by 1.

-The procedure from step 5 is to repeat the duration, where the pre-sequence code retransmission counter exceeds 0. When the retransmission counter reads 0, the higher layer (MAC) is notified of the fact that the ACK signal is not received on the AICH, and ends the random access control procedure in the physical layer.

7. If the NACK corresponding to the selected signature is detected in the relevant downlink access slot, the higher layer (MAC) is notified of the fact that the NACK has been received on the AICH, and the randomness in the physical layer is ended Access control procedures.

8. The random access message is based on the AICH transmission timing parameters, and 3 or 4 uplink access slots are transmitted after the uplink access slot of the previous sequence code is transmitted last. The transmission power of the control channel of the random access message is set at a level higher than the transmission power of the last preamble transmission by a power offset.

9. The higher layer is notified of the transmission of the random access message and ends the random access control procedure in the physical layer.

Figure 12 shows an exemplary signal flow used for signaling establishment.

Once the PRACH power control preamble has been confirmed, the RRC connection request message can be transmitted (S1201). It contains the reason for requesting the connection.

Depending on the reason for the request, the radio network decides the type of resources reserved, and implements synchronization and signaling establishment in the radio network node (ie, Node B and serving RNC) (S1202). When the radio network is ready, it sends a connection setting message conveying information about the radio resource to be used to the UE (S1203). The UE confirms the connection establishment by sending the connection setting complete message (S1204). When the connection has been established, the UE sends an initial direct transfer message, which may include various types of information, such as UE identification, current location, requested transaction type, and the like (S1205). Here, the current location can indicate the PLMN that the UE requests to establish a signaling connection. An exemplary list of information elements that can be carried by the initial direct transfer message is defined in 3GPP TS 25.331.

Then the UE and the network authenticate each other and establish a secure mode communication (S1206). The actual setting information is transmitted through the call control setting message (S1207). It identifies changes and indicates QoS requirements. When the message is received, the network starts the action for radio carrier allocation by checking whether there are enough resources to satisfy the requested QoS. If so, the radio carrier is allocated according to the request. Otherwise, the network can choose to continuously allocate with a reduced QoS value, or it can choose to queue the request until radio resources are available or reject the call request (S1208, S1209).

In a wireless system, a random access (executed on the RACH (Random Access Channel)) is a method used by the UE to initiate a call to establish signaling and short data transmission with the network.

In order to improve the spectral efficiency, a new uplink (transmission from a UE to the network) solution is under study within the 3GPP long-term evolution technology framework (framework). For the uplink, a multi-carrier (OFDMA) system or a single-carrier (localized or decentralized FDMA) system with cyclic prefix and frequency domain equalization can be a candidate. The different carriers can be distributed to the UEs. In these systems, a set of sub-carrier frequencies are assigned to each uplink communication link in a cell. The group of sub-carrier frequencies allocated to each communication link is selected from all the sub-carrier frequencies valid for the system. In order to achieve the goal of spectral efficiency, suppose a new wireless interface is reused at a frequency that achieves 1, as WCDMA does.

In this orthogonal system, the internal cell interference between carriers within the same cell does not occur. However, it is possible that internal cell interference occurs due to the use of the same sub-carrier frequency in neighboring cells.

In these systems, there is no method that can coordinate the allocation of sub-carrier frequencies to the RACH communication link based on interference coordination technology, so as to maximize the possibility of correct detection and minimize the error detection of random access sequences change.

In this way, this disclosure provides the following conceptual ideas. The first aspect of the present disclosure provides a method for selecting a RACH channel dedicated to random access. The method includes planning a set of uplink subcarrier groups (RACH channels, as described below) based on the path loss level or other measurements ). Other metrics related to path loss, such as SNR, received signal level (Rx level), interference level, etc., are all possible candidates.

Figure 13 shows an exemplary procedure according to the present disclosure. The processing steps between the UE (terminal) and the network are as shown.

The network transmits system information to the UE (step 1). The system information may include a list of PRACH, related signatures, path loss measurement information, and so on. Then, the UE performs measurement on the downlink (step 2). The UE selects the PRACH and/or transmission power according to the measurement result (step 3). Thereafter, the UE and the network cooperate to perform the access procedure (step 4). Here, the transmission power of the preamble can be optionally included. Then, the network performs the estimation of the uplink channel (step 5). The network selects the uplink transmission power and/or resources that are being configured (step 6). The network then transmits an indication of the uplink transmission power and/or frequency being used to the UE (step 7). The UE uses the uplink transmission power and/or resources being used (step 8). It is clear that additional and/or alternative steps can be performed.

Figure 14 shows an example of RACH frequency planning within a cell. The UEs located in certain parts of a single cell may have different degrees of path loss and different levels of carrier-to-interference ratio (C/I). Regarding a single cell, there can be three kinds of regions. That is, the central area can be used for UEs with low C/I but high path loss; a border (or surrounding) area can be used for UEs with high C/I but low path loss; and a middle area (that is, in the Between the central area and the boundary area) can be used for UEs with medium C/I and medium path loss. It is clear that more or less path loss and/or C/I levels can be used.

Here, we should note that the hexagon is only an exemplary nature representing the cell of a cell network. We can understand that the actual shape of these cells can change due to various factors, such as geographic location, signal usage, desired coverage area, and the like.

Figure 15 shows an example of RACH radio frequency (carrier) arrangement. The RACH frequencies (with indexes from 0 to N) can be divided into three sets (Set 1, Set 2, Set 3). These sets of RACH radio frequencies can be configured in (a) a localized way and (b) a decentralized way. It is clear that other types of configuration methods can be used.

Figure 16 shows an example of RACH frequency planning within a network deployment for frequency reuse. Referring back to Figures 14 and 15, the cells can have different configurations and be planned in a specific way. For example, cell 1 can have three areas; a central area can be used for UEs with high C/I but low path loss, a border area can be used for UEs with low C/I but high path loss, and a middle area can be used for UEs with low C/I but high path loss. Mid-C/I and mid-path lost UEs. Around cell 1, there can be six cells. The first set of cells (cells 2, 4, 6) may have a central area available for UEs with low C/I but high path loss, a border area available for UEs with medium C/I and medium path loss, and A middle area can be used for UEs with high C/I and low path loss. Similarly, the second set of cells (cells 3, 5, 7) can have a central area for UEs with medium C/I and medium path loss, and a border area for UEs with high C/I and low path loss. UE and an intermediate area can be used for UEs with low C/I and high path loss. The first and second sets of these cells can be replaced as shown. However, it is clear that the arrangement of other cells is also possible as with the additional and/or alternative regions of each cell.

Figure 17 shows an example of RACH frequency planning within a network configuration for fractional reuse. Here, the repeated use of partial fragments can be regarded as when each cell can be divided into three types of segments, each segment has a central area, a middle area, and a boundary area. The triplets (cells 1, 2, 3) can be planned as shown in Figure 17. The features of the present disclosure will be explained in more detail by referring to FIGS. 13 to 17.

The path loss expresses the attenuation experience (undergone) by the signal between the transmitter and the receiver. The signal is due to many effects such as the loss of distance from free-space and some due to reflection, refraction, and absorption. And so on, caused by the faded path. In the same manner as in the related art, the UE reads the power level used on the common preamble channel into the system information on a broadcast channel. The current winding interference level can also be read in in the same way. It measures the received power on the common preamble channel. By subtracting the received preamble power from the transmitted preamble power, an estimate of the path loss can be obtained.

<i>Path loss</i>_<i>dB</i>＝<i>T</i>_<i>x</i><i>level</i>－<i>R</i>_<i>x</i><i>level</i>

in<i>T</i>_<i>x</i><i>level</i>Is the effective power level (taking into account the maximum output power and all gains and losses, that is: the gain of the transmitted antenna, cable loss), and<i>R</i>_<i>x</i><i>level</i>Is the measured power level (taking into account the gain of the received antenna and the received level of interference).

Alternatively, the difference between the measurement of one of the target cells and the measurement of neighboring cells can also be used to determine on the RACH channel that can be used.

In addition to the set of valid RACH channels, the UE selects the set of allowed channels to be used, as shown below.<i>Set of RACH channels allowed</i>＝<i>f</i>(Any metric related to path loss or other measurement, such as one or more cells, valid RACH channel as described above)

In addition to the set of allowed channels, the UE can select a RACH channel according to any algorithm.

<i>RACH channel</i>＝<i>f</i>(The UE decides, for example, the hash function, random function, etc. on the UE-ID)

Together with the estimated path loss and interference power level, the UE can calculate the necessary transmission power required to achieve a certain SNR level on the network side. During the RACH procedure, indicate to the network the used Tx power/the range of the path loss or other measurements to allow the network to select the best uplink resource (ie frequency and/or time and/or Encoding patterns) are possible.

Another aspect of the present disclosure is to provide a specific RACH program. That is, the present disclosure can be implemented in the following ways.

A different RACH radio frequency or set of radio frequencies is planned inside the cell according to a specific criterion, which can be QoS, path loss, SNR, received signal level (Rx level), interference level, and so on. Different thresholds can be applied to different RACH resources. The specific threshold determines which RACH resources can be used. Then the UE selects one of the RACH resources according to a specified method to perform random access.

Some specific examples that can be applied to the present disclosure are as follows: The RACH channel can be passed in the frequency domain (for example, through a designated subcarrier), in the time domain (for example, by an instantaneous start and stop defined by the duration). ), in the code domain (for example, defined by a specified code sequence), or a combination of radio resources in the above mixed domains. For example, the RACH channel can use a combination of frequency and time division pattern, where the division pattern can be defined as a sequence of frequency and time slot. The frequency sequence is determined by a correspondence between frequency and radio frame for a RACH cell assigned to a specific UE in a given cell. A given RACH channel can use the same or different time slots in each radio frame. The time slot sequence is defined by a time slot number and/or frame number sequence. These parameters should be broadcast by the network (or derived from the broadcast parameters).

RACH resources in the frequency domain can be defined as a subset of M allowed frequencies, which are allocated from a larger group of N frequencies that are effective for communication links in the cell. The number M depends on the required RACH capacity and can be changed over time. For example, when the network detects that a random access channel is used, the used frequency can be removed from the allowed channel or It can only be marked as non-free or busy. On the network side, the subset of M allowed frequencies can be arranged according to the critical level if the path is missing, no matter in a localized manner (where the frequencies are grouped together to form part of the overall frequency band). Part) or in a dispersed manner (where the frequencies are equally spaced in the overall frequency band as shown in Figure 14). The path loss at a distance is known in order to follow a so-called distance power law, that is, the received signal is reduced to d^－^αAnd the extent of extension depends on the frequency band in use, the height and shape of the antenna, both the UE and the base station. Regarding path loss, there are a number of experimental models, among which OKUMURA &amp; HATA are the most well-known models. This model basically describes that the path loss increases as the distance increases. This means that the received signal intensity is greater than the neighboring part of the cell center and gradually decreases with the distance from the cell center. Therefore, on the network side, for a given frequency band, a given antenna height, and a given environment, the following very simple formula can be used to arrange M allowed frequencies according to several path loss levels:<i>Path loss dB</i>＝<i>C</i>＋<i>10α log d</i>

Where C is a constant, d is a distance and<i>α</i>It is the propagation exponent having a value dependent on the channel model, and is usually in the range of 2 to 4.

One of the main concepts of the present invention is that on the UE side, each UE loses the path of a received signal (SNR, received signal level (Rx level), interference level) in the downlink as shown in Figure 13 Standard) and use different RACH channels. Each UE in the cell estimates that the path is lost. Based on the estimated path loss, the UE determines which frequency subset is allowed to perform random access. This can be achieved by, for example, broadcasting the system information based on the threshold value, for example, giving the minimum/maximum measurement value to each RACH channel. Therefore, different frequencies or frequency sets can be used in this way to establish different groups of UEs, as shown in Figure 15.

The RACH resources in the time domain can be defined by a predetermined number of time offsets, which indicate when a UE can start the random access procedure. In this example, where the RACH resource is defined by the combination of the frequency domain and the time domain, the RACH channel can form M RACH allowed frequencies (as described above), which are mapped to the T RACH time offsets. This can be defined as having S time offsets on each allowed frequency on each cycle (the cycle can be one or more radio frames). In order to determine the S effective time offsets for each allowed frequency, the following formula can be applied:<maths><img file="TW200727614A_D0001.tif" /></maths>

Here, the mathematical symbol% is regarded as the so-called modulo operation, which returns the reminder after dividing by the divisor.

On the other hand, for every M allowed frequency cycles, each time offset can be defined so as to appear in C different frequencies. In order to determine which frequency it appears in, the following formula can be applied:<maths><img file="TW200727614A_D0002.tif" /></maths>

Here, the mathematical symbol% is regarded as the so-called modulo operation, which returns the reminder after dividing by the divisor.

The random access program may include the following components: in the chain, it consists of one or more pre-access codes (AP) and/or pre-collision codes (CP) and/or messages containing data and control information Partly composed. The pre-access sequence code is a predefined sequence called a signature. The valid access signature can be up to Z_m_a_x. All signatures can in principle be used for a random access (if not prohibited by the system). It is possible to detect several access attempts with different signatures at the same time, and to confirm them on the access indication channel (AICH) at the same time. The preamble of the collision detection can be sent for collision detection. The pre-collision detection code can be sent for collision detection before the message is transmitted. A collision detection signature can be shared with the access signature or completely different. Assuming that a collision detection pre-code is not used, a higher layer can be used to achieve (execute) collision resolution after receiving the message. It should be noted that assuming UE-based decisions, the AP and CP can carry additional information such as the channel to be used for transmission and the transmission power level. The current downlink interference level and so on.

In the downlink, one or more access instructions (AI) can be sent. The AI signal is transmitted from the network in response to the pre-access code detection. When operating properly, the network recognizes an access preamble from the UE and responds with an AI to establish a communication link. The access instruction is defined so that the access instruction can identify the signature to which it responds, and an implementation can prepare to use the identification signature sequence as the access-only preamble to which the response belongs. In the case of using the collision detection preamble, the collision indicator (CI) can be used to support the collision detection function. Similarly, if the AI uses the AP signature sequence in response, the CI can use the CD signature sequence. Additional information can be included in the AI (and CI), such as: the channel used for message transmission, the waiting time before the message transmission call time advance (TA), and the TA is used to derive the time advance The correct value of the value, where the UE must be used for the uplink transmission, the used transmission power level or the current uplink interference level, etc.

The random access procedure can be divided into several phases (phases A) to G) as shown below): A) The UE should start to listen to the broadcast channel in order to obtain RACH control parameters. The purpose of the RACH control parameters is to provide parameters for controlling the use of the RACH. These parameters should be any of the following: (1) Access Service Level (ASC) and related persistence values (such as the related field).

(2) A collection of effective RACH channels (or channel groups, these channels can be arranged in the time-frequency domain as described above).

(3) The RACH configuration index offset (RAIO) allows the calculation of the offset for the next RACH channel during the retransmission of the preamble (which can be regarded as the RACH jump).

(4) The sequence code parameters before access: a) A collection of valid access signatures. The same or different signatures can be configured in each RACH channel group.

b) The maximum number of retransmissions allowed.

c) It is used to calculate the minimum number of time offsets between the transmission of two preambles.

d) The power of the preamble, regardless of whether the power slope of the preamble is not used, can be the same for each preamble retransmission.

e) If the preamble power slope is used: i) the initial preamble power and ii) the power step between the preamble power.

(5) If collision resolution is performed in the physical layer, the pre-collision sequence code parameters may be like access pre-code parameters with the same or different parameter values.

(6) The power offset between the access (or collision) preamble part and the message part.

(7) Use the number of time offsets in the transmission of the expanded message part

(8) It can also indicate the current winding interference level.

(9) For each uplink channel, respond to the downlink measurement purpose (such as the minimum/maximum measurement value, where the measurement value can be path loss, SNR, received signal level (Rx level), interference level, etc. , Or the difference between the measured value between different cells, such as the difference between a cell with a RACH channel and a neighboring cell) give a critical value.

(10) The offset used in the calculation of the measured values, such as the difference between the current and the leading power of the neighboring cell, and so on.

B) The UEs measure the received power on the common preamble channel. By subtracting the received preamble power from the transmitted preamble power, it can obtain an estimate of the path loss. Based on the estimated path loss, the UE knows which RACH channel group is allowed to use.

C) The UE randomly selects one of the RACH channels from the group allowed to use it. What's more, the pre-access code signatures are randomly selected from the valid signatures.

D) A pre-access code is sent along with the selected signature. It may include additional information on the next RACH channel (assuming the UE-based decision), which RACH channel will be used for transmission, transmission power level, current downlink interference level, and so on.

E) The UE decodes the acquisition instruction (AI) to

F) Assuming that AI is not detected, the UE can choose another signature and if the power slope is used, the UE uses the steps given by the network to increase the transmission power of the access preamble; otherwise, it can be used as the preamble The code is retransmitted while maintaining the same power level. The access preamble can be retransmitted in the following situations: (1) in the next valid RACH channel from the group; (2) in the RACH channel according to RAIO (RACH configuration index offset); (3) In the same RACH channel as the previous transmission; (4) If not prohibited by the system, in the RACH channel from another group.

G) When AI is detected, the UE starts a detection preamble (if collision resolution is performed on the physical layer) or message transmission (if collision resolution is performed on a higher layer).

1) In the case of the pre-collision detection code, after detecting an AI, a CP with the same power level as the last AP will be transmitted along with another randomly selected signature. The CP can be transmitted in one of the RACH channels as described above (see previous point on retransmission of the access preamble). The network is expected to echo the CP signature on the CI, and in this way reduce the collision probability on the physical layer (L1).

2) The message part can be in the RACH channel according to one of the methods used for preamble transmission or can be in an AI or CI (see above for information that can be included in AI and/or CI). These additional information elements) are transmitted in another specific channel or by another network channel. The random access message is transmitted according to the number of time offsets to expand the transmission of the message part as instructed by the network. It should be noted that the HARQ method can be used for data block confirmation during this period.

The concepts and features of the present disclosure are not limited to wireless systems, but can also be applied to any communication system with an access protocol that can be used for communication resources.

In summary, the present disclosure provides the following features: a method for accessing an uplink channel may include estimating the quality of the received signal and selecting an uplink from a set of valid uplink channels based on the estimation result aisle. The UE can estimate the quality based on the preamble bit sent in the downlink. The UE can estimate the difference between the current and the quality of the neighboring cell. The network can send to the UE the quality range that must be measured by the UE in order to be allowed to access an uplink channel. A method for managing the use of different uplink channels may include the transmission of information on the demand for downlink measurement, which needs to be performed to enable access to a designated uplink channel.

The present disclosure provides a method for determining random access resources executed by a mobile terminal. The method includes at least the following steps: receiving information from a network on effective random access resources; The information received by the network determines how to derive the allowed random access resources; measures the received signal quality of at least one of a cell being accessed and a neighboring cell; and based on the decision Steps and measurement steps to derive the allowed random access resources.

The information received from the network can be received in a broadcast, multicast or proprietary manner. The received signal quality may include at least one of carrier/spectral noise density, signal-to-noise ratio, carrier/interference, and path loss energy. These random access resources may include: a set of any combination of time, frequency, and code. In the method, one of the RACH channels includes M RACHs that allow frequency mapping to the TRACH time offset. In this method, in each cycle, S time offsets of each allowed frequency are defined, and each cycle includes one or more radio frames. In this method, for every M allowed cycles, each time offset is defined in order to appear in C different frequencies. The method allows one or more effective random access resources to be used if a measurement of the received signal quality of at least one of the cell being accessed and the neighboring cell is greater than or less than a critical value . The method may further include the following steps: execute an access procedure, the procedure includes the step of transmitting an access burst (burst), which can be retransmitted according to the allowed random access resources and the selected random The access resource is used for this previous transmission. In the method, the retransmission access burst uses random access channel (RACH) hopping.

Similarly, the present disclosure provides a method for determining random access resources executed by a network. The method includes at least the following steps: transmitting information to a terminal on an effective random access resource; and transmitting and following the link One of the radio signals measures at least one related parameter to allow the terminal to decide how to derive the random access resources that are being allowed.

The method may further include the following steps: coordinating how the at least two random access resources are configured and/or how the at least one parameter for each random access resource is set. The random access resources are allocated in a localized or decentralized manner. The random access resources are configured according to the traffic load. The information is transmitted in a broadcast, multicast or proprietary way. The parameter may indicate that the measurement of the downlink radio signal includes at least one of carrier energy/spectral noise density, signal-to-noise ratio, carrier/interference, and path loss. These random access resources may include: a set of any combination of time, frequency, and code. In this method, one of the RACH channels includes M allowed frequency RACHs mapped on the T RACH time offsets. In each cycle, S time offsets of each allowed frequency are defined, and each cycle includes One or more radio frames. The method wherein the parameter indicates that if a measurement of the received signal quality of at least one of the cell being accessed and the neighboring cell is greater or less than a critical value, then one or more effective random accesses are allowed Resources can be used by the terminal.

Some relevant parts of the 3GPP specifications, such as 3GPP TS 22.011, 25.321, 25.331 (and its ongoing enhancements and other related paragraphs), are part of the specific embodiments of the present disclosure, and are hereby incorporated by reference. Part of this disclosure.

This specification describes various exemplary embodiments in the present disclosure. The scope of the patent application is intended to cover various modifications and equivalent configurations of the exemplary embodiments disclosed in the specification. Therefore, the scope of the following patent applications should be reasonably interpreted in the broadest sense to cover modifications, equivalent structures and features consistent with the spirit and scope of the features disclosed herein.

Figure 1 shows the radio interface protocol architecture based on the 3GPP radio access network standard.

Figure 2 shows an exemplary frequency-time representation of an OFDM signal.

Figure 3 shows an example of an access slot related to the transmission of the preamble, message, and retrieval instruction (AI).

Figure 4 shows an example of the number of RACH access slots and their spacing.

Figure 5 shows an example of receiving DL AICH and UL PRACH by the UE.

Figure 6 shows a table with available uplink access slots for different RACH secondary channels.

Figure 7 shows an exemplary format of the pre-code signature.

Figure 8 shows an exemplary structure of the random access message part.

Figure 9 shows an exemplary format (structure) of AICH.

Figure 10 shows a table showing the correspondence between AC and ASC.

Figure 11 shows a flow chart of an exemplary control access procedure.

Figure 12 shows an exemplary signal flow used for signaling establishment.

Figure 13 shows an exemplary procedure according to the present disclosure.

Figure 14 shows an example of RACH frequency planning within a cell.

Figure 15 shows an example of RACH radio frequency (carrier) arrangement.

Figure 16 shows an example of RACH frequency planning within a network deployment for frequency reuse.

Figure 17 shows an example of RACH frequency planning within a network configuration for fractional reuse.