Communication systems

Communication system (6)

Field of invention

Recently, it is of great importance for the use of multi-hop technology in packet radio and other communication systems. The purpose of this technology is to expand coverage and increase system capacity (throughput).

Background of the invention

In a multi-hop communication system, communication signals are transmitted along a communication path from a source device through one or more relay devices to a destination device. Figure 1 shows a single-cell dual-hop wireless communication system, which includes a base station BS (known as "Node-B" NB under the structure of a 3G communication system), and a relay node RN (also known as It is a relay station RS), and a user equipment UE (also known as a mobile station MS). In the case that a signal is transmitted from a base station via a relay node (RN) to a destination user equipment (UE) on the downlink (DL), the base station includes the source station (S) and the user equipment includes the destination Station (D). In the case that a communication signal is transmitted from a destination user equipment (UE) to a base station via a relay node on the uplink (UL), the user equipment includes the source station and the base station includes the destination station. The subsequent communication formation includes a signal transmitted by the user to identify itself to the base station (and to the network) as part of the network login process. This is particularly relevant to the present invention which will be explained below. A relay node is an example of an intermediate device and includes a receiver operable to receive data from the source device; and a transmitter operable to transmit data or its products to the destination device.

Simple analog repeaters or digital repeaters have been used to improve or provide coverage in blind spots. They can operate with different transmission frequency bands from the source station to avoid interference between the source transmission and the repeater transmission, or they can operate when the source station is not transmitting.

Figure 2 shows various applications of relay stations. For fixed public construction, the coverage area provided by the relay station can be "filled in" for the mobile station to access the communication network. The mobile station may be in the shadow of other objects or unable to receive even in the normal range of the base station. A signal of sufficient strength from the base station. The figure also shows "range expansion", where a relay station allows access when a mobile station is outside the normal data transmission range of the base station. An example of "fill in" shown in the upper right of Figure 2 is to place a wandering relay station to allow passage through the coverage area of a building that may be above, in, or below the ground.

Other applications are mobile relay stations, which are used for temporary coverage and provide access during incidents or emergencies/disasters. The last application shown at the bottom right of Figure 2 provides access to a network using a relay located in a vehicle.

Relay can also be used with advanced transmission technology to enhance the gain of the communication system, as described below.

The occurrence of conventional propagation loss, or "path loss" is covered by the dispersion or distortion of radio communication when it travels through space, resulting in weaker signal strength. The parameters that affect the path loss between the transmitter and receiver include: transmitter antenna height, receiver antenna height, carrier frequency, congestion type (urban, suburban, rural), morphological details such as height, density, spacing, terrain (hills) ,flat). The path loss L (dB) between the transmitter and the receiver can be modeled as:

<i>L</i>=<i>b</i>+10<i>n</i>log<i>d</i>(A)

Where d (meters) is the distance between the transmitter and the receiver, b (db) and n are the path loss parameters, and the absolute path loss value is<i>l</i>=10⁽^<i>L</i>^/10)。

The total absolute path loss experienced on the indirect link SI+ID may be less than the path loss experienced on the direct link SD, in other words it may be:

L(SI)+L(ID)&lt;L(SD) (B)

Divide a transmission link into two shorter transmission segments to take advantage of the non-linear relationship between path losses. From a simple theoretical analysis of the path loss using equation (A), it can be understood that when a signal is sent from a source device through an intermediate device (for example, a relay node) to a destination device rather than directly from the source device When it reaches the destination device, it can achieve a reduction in total path loss (and therefore improve or increase signal strength and data throughput). If implemented appropriately, a multi-hop communication system can reduce the transmitter's transmitting power to facilitate wireless transmission, thereby reducing interference and reducing exposure to electromagnetic radiation. Alternatively, the reduction in the overall path loss can be used to improve the quality of the signal received by the receiver without increasing the overall radiated transmission power required to transmit the signal.

The multi-hop system is suitable for multi-carrier transmission. In a multi-carrier transmission system, such as FDM (Frequency Division Multiplexing), OFDM (Orthogonal Frequency Division Multiplexing) or DMT (Discrete Multi-Modulation), a single data stream is modulated onto N parallel attached carriers, each A subcarrier signal has its own frequency range. This allows the total bandwidth (the amount of data transmitted in a given time) allocated to multiple subcarriers to thereby increase the duration of each data symbol. Because each subcarrier has a lower information rate. Each sub-carrier has a low information ratio. Compared with the single-carrier system, the advantage of the multi-carrier system is that it has stronger immunity to distortion caused by the channel. This is achieved by ensuring the transmission rate, and therefore the bandwidth of each subcarrier is smaller than the uniform bandwidth of the channel. Therefore, the channel distortion experienced on a signal subcarrier is frequency-independent and can therefore be corrected by a simple phase and amplitude correction factor. Therefore, when the system bandwidth exceeds the uniform bandwidth of the channel, the complexity of the channel distortion correction entity in a multi-carrier receiver can be lower than that of its counterpart in a single-carrier receiver.

Orthogonal Frequency Division Multiplexing (OFDM) is a modulation technology code based on FDM. An OFDM system uses multiple sub-carrier frequencies that are mathematically orthogonal so that the sub-carrier spectrum can overlap without interference due to the fact that they are mutually independent. The orthogonality of the OFDM system removes the need for guard band frequencies and therefore increases the spectrum efficiency of the system. OFDM has been proposed and adopted in many wireless systems. It has recently been used for asymmetric digital subscriber line (ADSL) connections, some wireless LAN applications (such as WiFi devices based on the IEEE802.11a/g standard), and (particularly regarding the present invention) such as WiMAX (based on the IEEE802.16 standard) The wireless MAN application. The application of OFDM is usually accompanied by channel coding, an error correction technique, to generate coded orthogonal FDM or COFDM. COFDM is now widely used in telecommunication systems to improve the performance of an OFDM-based system in a multipath environment, in which the variable of channel distortion can be regarded as a subcarrier across the frequency domain and symbols in the time domain. This system has been used for video and audio broadcasting, such as DVB and DAB, and certain types of computer network technology.

In an OFDM system, one block of N modulated parallel data source signals borrows an inverse discrete or fast Fourier transform algorithm (IDFT/IFFT) and maps it to N orthogonal parallel subcarriers to form it at the transmitter. A conventionally known signal is an "OFDM symbol" in the time domain. Therefore, an "OFDM symbol" is a compensation signal for all N subcarrier signals. An OFDM symbol can be expressed mathematically as:

<maths><img file="TW201028024A_D0001.tif" /></maths>

Where Δ<i>f</i>Is the subcarrier in Hertz, Ts=1/Δ<i>f</i>Is the symbol time interval in seconds, and c_nThe source signal is modulated. The subcarrier vector of each source signal above which is modulated in each program (1),<img file="TW201028024A_D0002.tif" />, C=(c₀, C₁..c_N-1) Is a vector of N cluster symbols from a finite cluster. At the receiver, the received time domain signal is converted back to the frequency domain by applying Discrete Fourier Transform (DFT) or Fast Fourier Transform (FFT) algorithms.

OFDMA (Orthogonal Frequency Division Multiple Access) is a multiple access variation of OFDM. Its action is by allocating a subset of subcarriers to a different user. This allows simultaneous transmission from several users resulting in better spectrum efficiency. However, there is still the problem of allowing two-way communication, that is, there is no interference in the upstream and downstream directions.

In order to carry out two-way communication between two nodes, there are two different conventional methods used to duplex these two communication links (forward or down-link and reverse or up-link) to overcome the equipment in the same resource The physical limitation on the media that cannot transmit and receive at the same time. The first is Frequency Division Duplex (FDD), which involves operating two links at the same time but in different frequency bands. The operation in different frequency bands is by subdividing the transmission medium into two different frequency bands, one for the feed chain The other is used for reverse link communication. The second type is Time Division Duplex (TDD), which involves using the same frequency band to access the two links, but further subdividing the time to access the media, so that only the forward or reverse link is used at any point in time media. The two methods (TDD&amp;FDD) have their relative advantages, and both are commonly used in single-hop wired and wireless communication systems. For example, the IEEE802.16 standard includes FDD and TDD modes.

For example, Figure 8 illustrates the single-hop TDD frame structure used in the OFDMA physical layer mode of the IEEE802.16 standard (WiMAX) as an example. Each frame is divided into DL and UL sub-frames, each as a discrete transmission interval. They are separated by transmit/receive and receive/transmit transition guard intervals (TTG and RTG, respectively). Each DL subframe starts with a prefix, followed by a frame control header (FCH), DL-MAP, and UL-MAP.

FCH contains the DL frame prefix (DLFP) to specify the length of the slave file and DL-MAP. DLFP is a data structure transmitted at the beginning of each frame and contains information about the current frame, which is mapped to FCH.

Synchronous DL configurations can be broadcast, multiplexed, and unicast, and they can also include configurations for another BS that is not the serving BS. Synchronous UL may be data configuration and range or bandwidth request.

The frame structure for multi-hop applications is disclosed in the cases of GB0616477.6, GB0616481.8, GB0616479.2, and P107297GB0 (as applied by the same date as this application and by the same applicant). These applications are also applied here, and their contents are for reference in this case.

When the modulation, transmission, reception, and demodulation processing of an information signal is performed in a communication system, the original signal is traditionally subjected to distortion. These distortions can include delay, frequency offset, and phase rotation, and can result in receiving multiple independent distortion copies of the original information. In order to correct these distortions in the receiver, general communication systems use special training sequences to transmit them through the channel so that they suffer the same distortion as the information signal. As long as these training sequences are found in the receiver, it can calculate the distortion used in the transmission process, and then correct the received information signal so that the distortion is minimized or completely removed. Therefore, this training signal can be used in the synchronization (time and frequency) of the receiver, as well as the channel evaluation and equalization phase.

It is possible to form a set of known training sequences for transmission in the communication system. Each sequence in the group is different from each other, so that the identity of the transmitter in the communication network with one of the multiple transmitters can be distinguished at the receiver. This allows the receiver to determine the properties of the transmitter and evaluate the transmitter and channel induced distortions that will be encountered on the signal received from a particular transmitter.

In a single-hop communication system (such as IEEE802.16e-2005), such a transmitted signal that can be used for identification and training is a prefix sequence. As its name suggests, it is transmitted at the beginning of each frame before transmitting data. An 802.16e-2005 single-hop user or mobile station (SS or MS) will use the prefix to perform some tasks, including transmitter identification used to determine ID cell parameters and segment numbers. It can also be used to synchronize with the transmitter (ie correct clock and frequency offset).

Therefore, in order to support MS or SS, a relay station can be requested to transmit a prefix to enable MS or SS to recognize, synchronize, and communicate with it. Since all the prefix transmissions from all transmitters (BS and RS) must be synchronized in time in a cellular network, this requirement makes an active RS unable to receive data from the network due to physical limitations that cannot simultaneously transmit and receive with the same transmission resource. The prefix sequence of a BS or another RS.

When operating a TDD network, it is also desirable that all transmitters be synchronized in time and frequency. This allows an MS to synchronize with a transmitter to automatically synchronize with all other transmitters in the network and thereby realize rapid delivery between transmitters (when synchronization is not required), and also perform macro-diversity operations, For example, the multi-BS MBS described in the IEEE802.16e-2005 standard receives control and data information from two different resources.

When the RS is preceded by a synchronized network, it further hopes that the transmission action is synchronized with the existing BS, so that the MS can continue to benefit from the associated synchronization network. Therefore, the RS and the BS should start their transmission at the same time, and they should both transmit their synchronization signals for the MS transmitter to recognize and synchronize in real time at the same time. Once the synchronization signal is transmitted in a single-frequency TDD network to synchronize the reception of the BS synchronization signal, this then disables the RS. Therefore, the RS has no reference that can be used to maintain synchronization with the BS (ie, transmit its own synchronization and identification signals) while being operational.

Reference is now made to the invention as defined by the independent item of the scope of the patent application. Further embodiments are defined by the appendix in the scope of the patent application.

Summary of the invention

The inventor of this case recognizes this limitation in RS and proposes a solution, which is about designing a new signal for BS or RS transmission, which can be received by RS so that RS can receive a standard prefix sequence and receive new signals , Enable transmitter identification, synchronization, and channel evaluation.

The solution to this problem in the embodiment of the present invention is to transmit a special BS-RS (or RS-RS when there are more than two hops) synchronization signal. If appropriate, this signal can also be an RS-MS signal. However, this signal should preferably have the property that it is not suddenly detected as the starting point of an error frame by an MS that does not know the fact that the BS or RS can transmit this "relay midfix".

The development of the present invention proposes a type of wave type for relay infix.

Schematic description

The preferred features of the present invention will now be described, completely by way of example, with reference to the accompanying drawings, in which: Figure 1 shows an RA zone and the definition of RA regions; Figure 2 shows an RA zone The use of transmission resources; Figure 3 shows the interaction between the transmitter and the network management entity; Figure 4 shows the interaction between a network-related RS and an operational network; Figure 5 shows the RA reception in the receiver And processing procedures; Figure 6 shows a single-cell dual-hop wireless communication system; Figures 7a-b show the application of a relay station; and Figure 8 shows a single unit used in the OFDMA physical layer mode of the IEEE802.16 standard Jump to the TDD frame structure.

Detailed description of the preferred embodiment

For example, Figure 8 shows a single-hop TDD frame structure used in the OFDMA physical layer mode of the IEEE802.16 standard, which indicates the standard that can be used by the MS to identify the distortion correction components of the BS and the training receiver Mandatory prefix sequence.

The embodiment of the present invention refers to a new signal, which is transmitted in another area of the DL subframe (the area where the prefix is not located). This signal can be in the middle of the DL sub-frame, thus forming an infix, or at the end of the sub-frame, thus forming a suffix. From now on, in order to unify the terminology, the new signal is referred to herein as a relay affix (RA) or an intermediate affix (RM).

<b>RA signal design</b>

RA requirements are similar to prefixes, which can be used by receivers to identify and distinguish the transmitter from other potential multiple transmitters in the communication system. It must also enable the receiver to evaluate or update an existing evaluation regarding the transmitter and channel induced distortion. It must not be suddenly recognized by an MS as a normal prefix sequence, because this will confuse the latent MS that does not yet know the existence of the relay prefix.

In order to meet the above requirements, it can be assumed that some different conventional mathematical sequences can be used to generate the relay affixes or relay affix groups used in the communication network.

Generally, the properties of the transmitted RA signal should therefore be:

Good auto-correlation properties: to use time/frequency offset judgments in the launch program;

A set of unique sequences can be formed: so that different sequences can be used to identify different transmitters (that is, provide an identification parameter that can be further used for the receiver);

Good interactive properties: to prevent false detection of time/frequency offset;

Low peak-to-average power ratio (PAPR) in the same time domain: Enables the use of non-linear amplifiers or the transmission power is higher than the standard data transmission power, based on the difference in PAPR between RA and data signals.

Nearly fixed or constant amplitude in the frequency domain: Provides a uniformly-surrounded transmit channel, and therefore improves the accuracy that can be achieved by the channel estimator in the receiver.

Low correlation with all general prefix sequences: avoid RA being mistakenly detected as a general prefix by a latent MS.

According to these requirements: PN (virtual noise) sequence can be used when used in IEEE802.16 standard; Golay sequence[4][5]; or CAZAC sequence (fixed amplitude and zero autocorrelation) (refer to [3] for more information on using CAZAC Sequence in training information), such as Chu[2] and Frank-Zadof[1] sequences to construct relay affixes. These sequences are all conventionally used to represent some or all of the required attributes, and therefore have been previously proposed to form such training or recognition sequences.

However, depending on the sequence type used for the normal prefix and the ability to provide a set of sequences with the aforementioned properties, it may not be possible to use all sequence types. For example, if the PN sequence is used as a general front ring, it will be found that it cannot generate a sufficient number of more PN sequences based on the attributes listed for the relay prefix group (such as low PAPR). In this case, it is more appropriate to use a set of different types of sequences to ensure that the selected trunk prefix group maintains the necessary attributes that are low in correlation with all general prefix sequences.

<b>RA transmission processing in BS or RS</b>

The BS or RS transmitting an RA will first determine the RA transmitting position in the following subframe. As mentioned earlier, the transmission can be anywhere within the frame. However, it can be assumed that certain general frames may be required to support relay [refer to GB0616477.6, GB0616481.8, GB0616479.2], which limits the flexibility of the transmitter to locate RA.

Once the position of the RA in the frame is determined, the transmitter then determines the number of transmission resources that will be allocated to the RA. Many factors will affect this decision: including a multi-cell transmitter to achieve effective frequency reuse, the need to reduce interference, and the amount of transmission resources that will be used by BS to RS or RS to RS data transmission to separate the same cellular The method of different transmitters operating at the same frequency in the network, and the type of sequence used to form RA.

One solution is to form an RA zone in the lower chain frame, as shown in Figure 1(a). All OFDM symbols here are reserved for RA transmission. Yet another way is to configure one of the sub-bands or regions of the downlink sub-frame for RA transmission, as shown in Figure 1(b).

If all frequency bands can be used for BS to RS or RS to RS data transmission, the former scheme is more appropriate, but the latter can be applied when the RA group is small or BS to RS or RS to RS data transmission only uses the total frequency transmission resources One part (namely the sub-band) does not require a complete symbol to minimize the amount of transmission resources required.

Once a zone or area is defined in the transmitter, the transmitter then determines the use of emission information in the zone or area. Many utilization schemes can be envisaged, including: all modulations are allocated to RA transmission, the total number of modulations is sampled so that RA is configured to each second, third, fourth, ... etc., a continuous modulation sub-band is Configuration. Each of these mechanisms is shown in Figure 2 illustrating the RA frequency band. It can also be extended to the RA area.

The advantage of the first scheme is that it can accurately evaluate the frequency channel when each tune is emitted by a conventional transmission, so that the distortion on each individual subcarrier can be determined. The advantage of the second scheme is that in a frequency reuse 1 scheme, sampling is adjusted and different sampling sequence offsets are used on different transmitters that can achieve effective frequency reuse greater than 1. The three-section setting can be an example, in which one of the initial load wave numbers is used for incremental offset on each section (that is, section 1 uses subcarrier {0, 3, 6, etc.}, section 2 uses {1, 4, 7, etc. }, and section 3 uses {2, 5, 8, etc.}) to apply a sampling factor of 3 to each section. The advantage of the third scheme is similar to the aforementioned scheme, which can achieve effective frequency reuse greater than 1 by assigning different sub-bands to different segments.

Now that the number and positions of available tunes available for the transmitter have been determined, the final stage is to generate training and recognition sequences that will be transmitted on the recognized tunes. As mentioned earlier, some different conventional sequences can be used for this purpose.

It is worth noting that in a synchronized cellular network, zone or area configuration may be performed in some network management entities (this may be located in the core network or in one of the transmitters). The same situation may exist when a specific sequence is assigned to a transmitter, especially when the sequence propagates inherent identification parameters. This network management entity can then ensure the harmony of the zones or regional locations of all transmitters in the cellular network. This in turn prevents interference between RA transmission from one transmitter and data transmission from another transmitter, especially when the RA transmission power increases due to its lower PAPR properties. It also ensures that the configuration of the identification parameters, from the receiver's point of view, is guaranteed not to receive the same identification from two visible transmitters (that is, there is sufficient space separation between reuse of the same identification sequence).

Finally, the transmitter (RS/BS) can include some signaling information in the broadcast message to indicate the existence and location of the RA zone or area, and it can also include a multiple broadcast or single broadcast message specifically directed to the RS Information is sent to inform the existence of RA.

In summary, Figure 3 provides a flow chart describing the interaction between the network management entity and the base station transmitting an RA. Figure 4 provides a flow chart describing the interaction between an RS that has entered a ready-to-operate network and the BS or RS that it attempts to associate. Finally, Figure 5 summarizes the RA reception and processing procedures in the receiver.

Another embodiment proposed by the present invention is further discussed with respect to the aforementioned Relay Interfix (RM) design, in which the same set of sequences used for the normal prefix is used. The advantage is that the best choice of a system can be used for both prefix and RM (there is no need to expand the prefix set and result in sub-optimal sequences, which means higher PAPR or good-to-bad correlation). The simpler way to distinguish the prefix and the RM is to transmit them at different levels of elevation during normal data transmission (or even without raising the RM transmission).

For example, in the IEEE802.16 standard, the prefix power should be raised 9dB higher than the average data rate. This scheme then sets the RM power to be 3dB lower than the prefix power. An MS or RS then scans the spectrum of a prefix, and an RM is visible. However, the prefix will always appear with a stronger correlation peak than the RM, and the prefix/RM pair from a BS or active RS will suffer the same path loss. Therefore, when determining a target, the MS (or the RS entering the network) will always lock the prefix transmission instead of the RM transmission.

It is also possible to further increase the robustness of this technology by changing the emissivity of the RM to be greater than one frame. It is expected that an MS in a specific period between the prefixes will also correctly detect the prefix instead of the RM as the frame start point.

The RM location can be dynamically controlled by transmitting a message contained in a normal (access link) transmission period (ie, BS or RS to MS) or a dedicated RS (relay link) transmission period.

Note that it is not necessary to send an RM all the time. Two mechanisms can be defined to determine whether to transmit an RM.

1. The BS detects through the uplink transmission that an RS is slowly losing synchronization with the BS. BS can keep correcting this problem through closed loop processing. However, if the transmission load on the BS-RS (or RS-RS) link exceeds an RM transmission management amount, the BS (or RS) may decide to start transmitting RM to assist the RS in maintaining synchronization.

2. RS can explicitly request to transmit RM to assist its synchronization. This request can be provided statically during the network login (that is, to indicate the ability negotiation that it wants/requires, or through a partial registration request, etc.). It can also indicate its requirements on the RM at this stage, such as the frequency at which it needs to be transmitted. In addition, it can move around and when needed, through a configuration request message. The method described below can be used by having high-quality crystals or using other technologies to maintain good synchronization (for example, using a periodic repetition structure of a periodic prefix in an OFDMA symbol) to become an initial stand-by RS with mobility. It is also required by an RS that wants to collect information about its neighboring signal strength. Again, the RS can dynamically request the frequency at which it needs the RM to be transmitted.

<b>Table 1: Relay infix attributes</b>

<tables><img file="TW201028024A_D0003.tif" /></tables>

<b>Overview of advantages</b>

In summary, the advantages of the embodiments of the present invention are:

When an RS cannot receive the identification and training information generated for use by the MS, keep it synchronized with a BS or another RS (in time &amp; frequency).

Let an RS use the sequence to update its evaluation of channel status information.

Prevent the operation of a latent MS (that is, not designed to be an operator in a relay system) from being interrupted by the transmission of further training and identification signals.

Let an RS scan and monitor the quality of the signal received from another nearby BS or RS that it may potentially be associated with.

In addition, the advantages of other embodiments of the present invention are as follows:

The existing prefix sequence group defined for the synchronization of MS to BS and MS identification of BS can be reused.

Provide a robust and minimal mechanism to help RS synchronization and transmitter identification.

Two mechanisms are provided to determine whether to launch RM.

The embodiments of the present invention can be implemented by hardware, or a software module running on one or more processors, or a combination thereof. That is, those skilled in the art will understand that a microprocessor or a digital signal processor (DSP) can be used to implement some or all of the functions of a transmitter of the embodiment of the present invention. The present invention can also implement one or more devices or equipment programs (such as computer programs and computer program products) to implement part or all of the methods described in this specification. Such programs embodying the present invention can be stored on a computer-readable medium, or can be presented in the form of one or more signals. Such signals can be data signals that can be downloaded from an Internet website, or can be provided by a carrier signal, or presented in any form.

<b>refer to</b>

[1] Frank RL, Zadoff SA. Phase shift coding with good period correlation properties. October 1962, IEEE Transformation in Information Theory, page 381-2.

[2] Chu DC. Polyphase coding with good period correlation properties. July 1972, IEEE Transformation in Information Theory, page 531-2.

[3] Milewski A. A periodic sequence of optimization attributes with channel evaluation and quick start equalization. Pages 426-31 of the IBM Research and Development Journal, September 1983.

[4] MJE Golay, "Multislit spectroscopy" J. Opt. Soc. Amer., 39, pp. 437-444, 1949.

[5] MJE Golay, "Complementary series" IRE Trans. Inform. Theory, IT-7, p. 8287, April 1961.

<b>Possible application of relay infix to IEEE standard 802.16: contribution of relay infix</b>

This contribution includes a technical proposal for a relay terminator, which can be selectively transmitted by an MR-BS or RS during the R-DL period. This infix can be received by an RS instead of the prefix transmitted in the access link when the RS transmits its own prefix.

<b>introduction</b>

When the BS and RS operate in a frame time synchronization mode [1], the RS cannot receive the prefix transmission of a TDD system, because they also need to transmit the prefix to support the SS connection defined in IEEE standard 802.16.

Therefore, this proposal defines a new relay prefix, which can be transmitted by a BS or RS during the R-link transmission period to replace the prefix received by an RS during the link period.

The infix is designed to have attributes that are very similar to the normal prefix so as to minimize the impact on the current standard, and it can also reuse the current technology defined for the MS receiver of the RS receiver.

<b>Relay infix (RM) attributes</b>

The attributes of the relay infix are summarized in Table 1.

<tables><img file="TW201028024A_D0004.tif" /></tables>

In summary, the sequence used for the relay infix is the same as the sequence used for the prefix. The two differences are that the power of each tune is increased by +6dB higher than the power of the unboosted data subcarrier, and the position of the RM is flexible [1]. Therefore, a simple related function is presented in SS, selecting RM from the prefix as the starting point of the frame candidate and selecting the link channel during network login.

Table 2 compares the power increase difference between various data and leading modulation types.

The existence of RM is controlled by BS. The choice of RS request to transmit an RM is left FFS. However, suppose that the first of the two mechanisms is a static request for an SBC message that requires RM to operate during network login, and the second is an unsolicited MAC management message from RS to BS. Dynamic request.

<tables><img file="TW201028024A_D0005.tif" /></tables>

<b>Proposed text change</b>

<b>Insert a new subclause at the end of section 8.4.6.1.1 as follows:</b>

8.4.6.1.1.3 Relay Infix (RM)

The BS or RS can also transmit RM during the R-DL transmission period to facilitate RS synchronization and be recognized by other RSs.

The subcarrier group and string used to modulate the RM preamble shall be the same as those defined for the prefix in 8.4.6.1.1. The modulation used for the RM preamble is the elevated BPSK as defined in 8.4.9.4.3.3.

<b>Insert a new subclause 8.4.9.4.3.3:</b>

8.4.9.4.3.3 Relay midfix modulation

The preamble in the RM on the R-DL should follow the instructions in 8.4.6.1.1.3 and should be adjusted according to equation (137a):

<maths><img file="TW201028024A_D0006.tif" /></maths>

Im(<i>RMPilotsModulated</i>)=0

<b>At the end of Section 8.4.10.1, insert a new subclause as follows:</b>

8.4.10.1.3 RS synchronization

In order to realize TDD and FDD, it is recommended that RS be synchronized in time with a common clock signal that is also used for BS synchronization, as described in section 8.4.10.1.1. The clock signal should be a 1pps clock and a 10MHz frequency reference. These signals are traditionally provided by a GPS receiver. In the event that the reference cannot be obtained from a shared reference, the RS can use the RM transmission from a BS or one of the other RSs, as described in 8.4.6.1.1.3. to maintain synchronization. In an event where the BS or RS does not provide a network clock signal, the RS should continue to operate. The RS should automatically resynchronize the network clock signal when the network clock signal is available.

To implement FDD and TDD, the frequency reference derived from the clock reference can be used to control the frequency accuracy of the RS so that they meet the accuracy requirements of 8.4.14. This is applied during normal operation and during periods when there is no clock reference.

<b>Insert the following text at the end of Section 8.4.14.1:</b>

In RS, both the transmitter center frequency and sampling frequency should be derived from the same reference oscillator. The accuracy of the reference frequency at the RS should be better than ±2ppm, and the RS uplink transmission should be locked to the BS so that its center frequency will not deviate from the subcarrier spacing of more than 2% compared to the BS center frequency. The RS downlink transmission should be locked to the BS so that its center frequency will not deviate from the subcarrier spacing by more than 2% compared to the BS center frequency.

<b>refer to</b>

[1] Hart, M et al., IEEE802.16 meeting #46, IEEE C802.16j-06/138, "Frame Structure for Multi-hop Relay Support" in Dallas, November 2006.

Figure 1 shows the definition of an RA zone and RA area;

Figure 2 shows the utilization of transmission resources in an RA zone;

Figure 3 shows the interaction between the transmitter and the network management entity;

Figure 4 shows the interaction between a network-related RS and an already operational network;

Figure 5 shows the RA receiving and processing procedure in the receiver;

Figure 6 shows a single-cell dual-hop wireless communication system;

Figures 7a-b show the application of a relay station; and

Figure 8 shows a single-hop TDD frame structure used in the OFDMA physical layer mode of the IEEE802.16 standard.