TWI416894B - Hybrid orthogonal frequency division multiple access system and method - Google Patents

Abstract

The system has a receiver with a common subassembly for processing received data to recover data mapped to subcarriers using orthogonal frequency division multiple access (OFDMA). A spread OFDMA subassembly is provided for recovering an input data. A non-spread OFDMA subassembly (140) is provided for recovering another input data. The subcarriers and time periods allocated to users are hopping in a pseudo-random way for the sub carriers allocated for non-spread orthogonal frequency division multiple access. An independent claim is also included for a method for transmitting data using hybrid orthogonal frequency division multiple access (OFDMA). -

Description

Hybrid orthogonal frequency division multiple access system and method

The present invention is related to wireless communication systems. More particularly, the present invention relates to a hybrid orthogonal frequency division multiple access system and method.

Future wireless communication systems will be expected to provide broadband services like access to the user's wireless Internet. This wideband service requires reliable and high throughput transmission over a wireless channel, which is typically time displeased and frequency selective. The wireless channel is limited by internal symbol interference (ISI) caused by limited spectrum and multipath fading. For next-generation wireless communication networks, Orthogonal Frequency Division Multiplexing (OFDM) and Orthogonal Frequency Division Multiple Access (OFDMA) are the most promising solutions.

The orthogonal frequency division multi-tool has high spectral efficiency because the subcarriers used in the orthogonal frequency division multiplexing system overlap in frequency, and a suitable modulation coding scheme (MCS) can be utilized throughout the subcarriers. In addition, the implementation of orthogonal frequency division multiplexing is simple because the baseband modulation and demodulation can be performed using simple inversion fast Fourier transform (IFFT) and fast Fourier transform (FFT) operations. Other advantages of this orthogonal frequency division multiplexing include a simple receiver structure and excellent robustness in a multipath environment.

Orthogonal frequency division multiplexing and orthogonal frequency division multiple access have been adopted by many wireless/wireline communication system standards, such as digital sound broadcasting (DAB), digital terrestrial sound broadcasting (DAB-T), IEEE 802.11a. /g, IEEE 802.16, Asynchronous Digital Subscriber Line (ADSL), and is considered for the third generation of Partnership Project (3GPP) Long Term Development (LTE), Code Division Multiple Access 2000 (CDMA 2000) development, fourth generation (4G) adopted in wireless communication systems, IEEE 802.11n, etc.

The main problem of orthogonal frequency division multiplexing and orthogonal frequency division multiple access is that it is difficult to eliminate or control internal cell interference to achieve a frequency reuse factor. The manner in which frequency hopping between cells and sub-media carrier allocation cooperation has been proposed to eliminate internal cell interference. However, the efficiency of both methods is limited.

The present invention is related to a hybrid orthogonal frequency division multiple access (OFDMA) system and method. The system includes a transmitter and a receiver. The transmitter includes a first unfolding orthogonal frequency division multiple access sub-assembly, a first non-expansion orthogonal frequency division multiple access sub-assembly, and a first common sub-assembly. The first expanded orthogonal frequency division multiple access sub-assembly expands the input data and maps the expanded data to a first sub-carrier group. The first non-expansion orthogonal frequency division multiple access sub-assembly maps the input data to a second sub-carrier group. The first common sub-assembly maps input data of the first and second sub-carrier groups by orthogonal frequency division multiple access transmission. The receiver includes a second unfolding orthogonal frequency division multiple access sub-assembly, a second non-expansion orthogonal frequency division multiple access sub-assembly, and a second common sub-assembly. The second common sub-assembly receives data using orthogonal frequency division multiple access processing to recover data mapped to the sub-carrier. The second unfolding orthogonal frequency division multiple access sub-assembly recovers the first input data by expanding user data in the code domain, and the second non-expansion orthogonal frequency division multiple access sub-component is used The second input data is restored.

Hereinafter, the terms "transmitter" and "receiver" include, but are not limited to, a user configuration (UE), a wireless transmission receiving unit (WTRU), a mobile station, a fixed or mobile subscriber unit, a pager, a node B, A base station, location controller, access point, or any form of device that has the ability to operate in a wireless environment.

Features of the invention may be combined in an integrated circuit (IC) or in a circuit comprising a plurality of interconnected units.

The present invention can be applied to any wireless communication system using orthogonal frequency division multiple access (or orthogonal frequency division multiplexing) and/or code division multiple access (CDMA), such as IEEE 802.11, IEEE 802.16, and third generation. (3G) cell-based systems, fourth-generation (4G) systems, satellite communication systems, and the like.

1 is a block diagram of an exemplary hybrid orthogonal frequency division multiple access system 10 in accordance with the present invention, including a transmitter 100 and a receiver 200. The transmitter 100 includes an unfolded orthogonal frequency division multiple access sub-assembly 130, a non-expansion orthogonal frequency division multiple access sub-assembly 140, and a common sub-assembly 150. In the expanded orthogonal frequency division multiple access sub-assembly 130, the input material 101 (for one or more users) is developed using a development code to generate a plurality of wafers 103, which are then mapped. To subcarriers. In the non-expansion orthogonal frequency division multiple access sub-assembly 140, input bits 111 (for one or more users) are mapped to subcarriers without expansion.

The expanded orthogonal frequency division multiple access sub-assembly 130 includes a spreader 102 and a first subcarrier expansion mapping unit 104. The non-expansion orthogonal frequency division multiple access sub-assembly 140 includes a serial sequence repeat (S/P) converter 112 and a second subcarrier mapping unit 114. The common sub-assembly 150 includes an N-dot inverse discrete Fourier transform (IDFT) processor 122, a sequence-to-serial train (P/S) converter 124, and a cyclic prefix (CP) insertion unit 126.

Suppose there are N subcarriers in the system, and there are K different users communicating in the system at the same time, and between the K users, the data is transmitted through the expanded orthogonal frequency division multiple access sub-assembly 130. To K _S users. In the deployed multiple access OFDM sub-assembly 130 to expand the non-orthogonal multiple access number of sub-carrier frequency sub-assembly 140 is used with a N _O N _S, respectively. The values of N _S and N _O satisfy 0 N _S N , 0 N _O N and N _S + N _O The condition of N.

The input data 101 is expanded by the expander 102 to a plurality of wafers 103. The chip 103 is then mapped by the subcarrier expansion mapping unit 104 to the N _S subcarriers. The expansion can be performed in the time domain, in the frequency domain, or both. For a particular user, the expansion factors in the time domain and the frequency domain are SF _t and SF _{f , respectively} . The joint expansion factor for the user is SF _{jo int} , which is equal to SF _t × SF _f . When SF _t =1, the expansion is performed only in the frequency domain, and when SF _f =1, the expansion is performed only in the time domain. The frequency domain expansion for user i is limited by the number of subcarriers N _S ( i ) assigned to the user i. The allocation of the subcarriers can be static or dynamic. In the case of N _S ( i )= N _S for each user i, the expanded orthogonal frequency division multiple access becomes an orthogonal frequency division multiplexing.

In the expanded orthogonal frequency division multiple access sub-assembly 130, one subcarrier can be mapped to more than one user. In this case, the input data 101 of two or more users mapped to the same subcarrier becomes code multiplexed and should therefore be developed with different expansion codes. If the expansion is performed in both the time and frequency domains, the expansion code assigned to the user in the time domain, the frequency domain, or both will be different.

Figure 2 shows an example of frequency domain expansion and subcarrier mapping in accordance with the present invention. The input data 101 is multiplexed by a multiplexer 202 with a development code 204 to produce a plurality of wafers 103'. The wafer 103' is converted to a sequence wafer 103 by a serial to serial converter 206. Each of the sequence wafers 103 is then mapped by the subcarrier mapping unit 104 to one of the subcarriers before being transmitted to the inverted discrete Fourier transform processor 122.

Figure 3 shows another example of frequency domain expansion and subcarrier mapping in accordance with the present invention. Instead of the unwinding process of the unwinding code by a spreader, each of the input data 101 is repeated a number of times at a wafer ratio using a repeater 302 to produce the wafer 103'. The wafer 103' is then converted to a sequence wafer 103 by a serial to serial sequence converter 304. Each of the sequence wafers 103 is then mapped by the subcarrier mapping unit 104 to one of the subcarriers before being transmitted to the inverted discrete Fourier transform processor 122.

Alternatively, when the input data is expanded in the time domain, each input data is expanded by a expander to produce a plurality of wafer streams, which are then mapped to the subcarriers. In this case, the time domain expansion can also be performed by simply repeating the input data without using a development code.

The common pilot can be transmitted on the subcarriers used in the spread orthogonal frequency division multiple access sub-assembly 130. In order to distinguish from other user data, the common guidance can also be expanded.

Referring again to FIG. 1, in the non-expansion orthogonal frequency division multiple access sub-assembly 140, input bits 111 of different users are converted by the serial to serial sequence converter 112 into sequence bits 113. The subcarrier mapping unit 114 allocates the user to one or more subcarriers, so each subcarrier is used by at most one user, and the bit from each user is mapped by the subcarrier mapping unit to the use. Subcarriers. In the sub-method, the user is multiplexed in the frequency domain. The number of subcarriers allocated to user i is denoted as N _O ( i ), and 0 N _O ( i ) N _O . This subcarrier allocation can be static or dynamic.

In accordance with the present invention, the non-expansion orthogonal frequency division multiple access sub-assembly 140 can perform time-frequency hopping in each cell in a quasi-random manner. By time domain hopping, the user transmitting in a cell changes over time (in other words, in one or more orthogonal frequency division multiplex symbols or frames). By frequency domain hopping, allocating to a cell for transmitting the user's subcarriers, jumping at each or several orthogonal frequency division multiplex symbols or frames. In this method, internal cell interference between the user and the cell can be eliminated and averaged.

Figure 4 shows an example of a time-frequency hopping according to the invention, which uses 10 sub-carriers s0-s9 during the time period of T0-T6. As an example, in Figure 2, subcarriers s3, s5, s8 are used to develop orthogonal frequency division multiple access, while the remaining subcarriers are used for non-expansion orthogonal frequency division multiple access. For subcarriers allocated to non-expansion orthogonal frequency division multiple access, the subcarriers allocated to the user and the time period are hopped in a quasi-random manner. For example, the data for user 1 is transmitted through s9 at T0, s7 at T1, s7 at T3, s1 and s9 at T4, and data for user 2 at S0 through s4 at T1. Pass s6, pass s3 at T2, and transmit s0 and s4 at T4. Therefore, it transmits data to different users through different orthogonal frequency division multiplex symbols or frames, and eliminates internal cell interference.

Referring again to FIG. 1, the wafer 105 and the data 115 are provided to the inverted discrete Fourier transform processor 122. The inverted discrete Fourier transform processor 122 converts the wafer 105 and the data 115 into time domain data 123. The inverted discrete Fourier transform processor 122 can be executed using Inverted Fast Fourier Transform (IFFT) or equivalent operations. The time domain data 123 is then converted by the serial to serial converter 124 into a serial data 125. A cyclic prefix (also known as a guard period (GP)) is then added by the cyclic prefix insertion unit 126 to the serial data 125. The wireless channel 160 is then transmitted over the data 127.

The receiver 200 includes an unrolled orthogonal frequency division multiple access sub-assembly 230, a non-expanded orthogonal frequency division multiple access sub-assembly 240, and a common sub-assembly 250 for orthogonal frequency division multiple access. The common sub-component 250 includes a cyclic prefix removal unit 202, a serial to serial sequencer 204, an N-point discrete complex leaf transform (DFT) processor 206, an equalizer 208, and a subcarrier demapping unit 210. . The expanded orthogonal frequency division multiple access sub-assembly 230 includes a code domain user separation unit 214 and the non-expansion orthogonal frequency division multiple access sub-assembly 240 includes a sequence-to-serial converter 216.

The receiver 200 receives the data 201 transmitted through the channel. The cyclic prefix removal unit 202 removes the cyclic prefix from the received material 201. After the cyclic prefix is removed, the data 203, which is time domain data, is converted by the serial to serial sequencer 204 into sequence data 205. The sequence data 205 is provided to the discrete Fourier transform processor 206 for conversion to frequency domain data 207, which means N sequence data on N subcarriers. The discrete complex leaf transform can be performed by a fast Fourier transform or an equivalent operation. The frequency domain data 207 is provided to the equalizer 208 and performs data equalization on each subcarrier. As in conventional orthogonal frequency division multiplexing systems, a simple one-tap equalizer can be used.

After equalizing each subcarrier, the data corresponding to a particular user is separated by the subcarrier demapping unit 210, which is a counter performed by the subcarrier expansion mapping unit 104, 114 at the transmitter 100. To operate. In the non-expansion orthogonal frequency division multiple access sub-assembly 240, the serial to serial train converter 216 simply converts each user profile 211 into a serial data 217. In the expanded orthogonal frequency division multiple access sub-assembly 230, the data 212 on the separated subcarriers is further processed by the code domain user separation unit 214. Depending on the manner of deployment at the transmitter 100, corresponding user separation is performed in the code domain user separation unit 214. For example, if the expansion is performed only in the time domain at the transmitter 100, a conventional 组合 type combiner can be used as the code domain user separation unit 214. If the expansion is performed only in the frequency domain at the transmitter 100, a conventional (frequency domain) despreader can be used as the code domain user separation unit 214. If the transmitter 100 is performing expansion in both the time domain and the frequency domain, a time-frequency multiplexer can be used as the code domain user separation unit 214.

Figure 5 is a block diagram of an exemplary time-frequency 组合 combiner 500 configured in accordance with the present invention. The exemplary time-frequency combiner 500 performs processing in both the time domain and the frequency domain to recover data that is unfolded in the time domain and the frequency domain of the transmitter 100. It should be noted that the time-frequency combiner 500 can also be implemented in different manners. The configuration provided in FIG. 5 is merely an example and is not a limitation, and the present invention is not limited to the structure shown in FIG. .

The time-frequency 组合 combiner 500 includes a de-expander 502 and a 组合-type combiner 504. For a particular user, the subcarrier demapping unit 210 in FIG. 1 is delivered to the despreader 502 for exploiting the separated data 212 collected by the orthogonal frequency division multiple access sub-assembly 230. The despreader 502 performs frequency domain despreading of the data 212 on the subcarriers. The despreader 502 includes a plurality of multiplexers 506 for multiplexing the data 212 expansion code conjugate 508, a summation 512 for summing the multiplication outputs 510, and for normalizing the summed output. The normalizer 516 of 514. The despread output 518 is then processed by the mashup combiner 504 to recover the user's profile using a time domain combination.

Referring again to FIG. 1, the transmitter 100, the receiver 200, or both may include multiple antennas, and may perform hybrid orthogonality in accordance with the present invention using multiple antennas on the transmitter side, the receiver side, or both Divided multiple access.

Although the features and elements of the present invention have been described in a particular combination of the preferred embodiments, each of the features and elements may be used alone or in combination with other features and elements of the present invention, or with other features and elements of the present invention. Different combinations are made together or separately. .

10. . . Hybrid orthogonal frequency division multiple access system

101. . . Input data

103, 103 ' , 105. . . Wafer

111. . . Input bit

113. . . Sequence bit

115, 127, 201, 203, 209, 212. . . data

123. . . Time domain data

125,217. . . Serial data

202. . . Multiplexer (Figure 2)

204. . . Expansion code (Figure 2)

205. . . Sequence data

207. . . Frequency domain data

211. . . User profile

500. . . Time frequency 组合 combiner

502. . . Decompressor

506. . . Multiplexer

508. . . Conjugate

510. . . Total multiplication output

514. . . Total output

518. . . Unrolling the output

CP. . . Cyclic prefix

IDFT. . . Inverted discrete complex leaf transform

OFDMA. . . Orthogonal frequency division multiple access

P/S. . . Sequence repeat column

S0~s9. . . Subcarrier

S/P. . . Serial sequence

T0~T6. . . Time period

1 is a block diagram of an exemplary hybrid orthogonal frequency division multiple access (OFDMA) system configured in accordance with the present invention.

Figure 2 shows an example of frequency domain expansion and subcarrier mapping in accordance with the present invention.

Figure 3 shows another example of unfolding and subcarrier mapping in accordance with the present invention.

Figure 4 shows an example of subcarrier time frequency hopping in accordance with the present invention.

Figure 5 is a block diagram of an exemplary time-frequency 组合 combiner configured in accordance with the present invention.

10. . . Hybrid orthogonal frequency division multiple access system

101. . . Input data

103, 105. . . Wafer

111. . . Input bit

113. . . Sequence bit

115, 127, 201, 203, 209, 212. . . data

123. . . Time domain data

125,217. . . Serial data

205. . . Sequence data

207. . . Frequency domain data

211. . . User profile

CP. . . Cyclic prefix

IDFT. . . Inverted discrete complex leaf transform

OFDMA. . . Orthogonal frequency division multiple access

P/S. . . Sequence repeat column

S/P. . . Serial sequence

Claims (13)

A Node B configured to perform Hybrid Orthogonal Frequency Division Multiple Access (OFDMA) communication, comprising: a transmitter comprising: an unfolding orthogonal frequency division multiple access sub-assembly configured to expand multi-user input data to Generating a multi-user expansion input data; the expanding orthogonal frequency division multiple access sub-component is configured to map the multi-user expansion input data to a first subcarrier group; a non-expansion orthogonal frequency division multiple access a subcomponent configured to map the non-expanded input data to a second subcarrier group; and the transmitter is configured to transmit the multiuser on the first subcarrier group and the second subcarrier group, respectively The input data and the non-expanded input data are expanded as part of the hybrid OFDMA symbol transmission. The Node B of claim 1, wherein the expanded orthogonal frequency division multiple access sub-assembly expands the multi-user input data in at least one of a time domain and a frequency domain. The Node B of claim 1, wherein the expanded orthogonal frequency division multiple access sub-assembly expands the multi-user input data by repeating a single user input data at a wafer ratio. The Node B of claim 1, wherein the expanded orthogonal frequency division multiple access sub-assembly and the non-expanded orthogonal frequency division multiple access sub-component dynamically map subcarriers. The Node B of claim 1, wherein the expanded orthogonal frequency division multiple access sub-assembly transmits a common guide on the first sub-carrier group. The node B according to claim 1, wherein the non-expansion orthogonal frequency division multiple access sub-component performs a time domain hopping and a frequency domain by mapping the non-expanded input data into the second subcarrier group. Jump at least one of them. The node B of claim 1, wherein the transmitter comprises multiple antennas. A method for mixing orthogonal frequency division multiple access (OFDMA) in a Node B, the method comprising: expanding a multi-user input data to generate a multi-user expansion input data; mapping the multi-user expansion input data to a a first subcarrier group; mapping the non-expanded input data to a second subcarrier group; and transmitting the multi-user expansion input data on the first subcarrier group and the second subcarrier group, respectively The non-expanded input data is transmitted as part of the hybrid OFDMA symbol. The method of claim 8, wherein the multi-user input data is expanded in at least one of a time domain and a frequency domain. The method of claim 8, wherein the multi-user input data is developed by repeating a single user input data at a wafer ratio. The method of claim 8, wherein the first and second subcarrier groups are dynamically mapped. The method of claim 8, wherein a common guide is transmitted on the first subcarrier group. The method of claim 8, wherein the mapping of the non-expanded input data to the second subcarrier group is performed using at least one of a time domain hop and a frequency domain hopping.