TW201029369A - Multi-user package for OFDM - Google Patents

Abstract

The invention relates to a multi-user package for OFDM. The multi-user package of the invention includes a plurality of user packages. Each user package includes a first pilot series group, a data subcarriers and a second pilot series group. The first pilot series group of the i-th user package overlaps the second pilot series group of the (i-1)-th user package, and the second pilot series group of the i-th user package overlaps the first pilot series group of the (i+1)-th user package. Because the pilot series group of the multi-user package is transmitted by the overlapping method, the bandwidth efficiency of the system of the invention can not be reduced. Furthermore, the multi-user package of the invention provides better carrier frequency synchronization and channel estimation performance than conventional multi-user package. Moreover, the multi-user package of the invention also has multi-user interference reduction utility.

Description

201029369 VI. Description of the Invention: [Technical Field of the Invention] The present invention relates to a multi-user data packet for an orthogonal frequency division multiplexing system. [Prior Art] Referring to Figure 1, there is shown a schematic diagram of a conventional orthogonal frequency division multiplexing system multi-user data package. The conventional orthogonal frequency division multiplexing system multi-user data packet 10 includes: a plurality of user data packets 11, 12, 13, and the like. According to the user's sorting direction ❹, each user data packet has a first pilot signal, a user data signal and a second pilot signal. The first user data packet 11 has a first pilot signal 111, a user data signal 112, and a second pilot signal 113. The i-th user data packet 12 has a first pilot signal 121 and a user data signal. 122 and a second pilot signal 123; the i + 1 user data packet 13 has a first pilot signal 131, a user data signal 132 and a second pilot signal 133. In the above-mentioned conventional multi-user orthogonal frequency division multiplexing system, the pilot signals are usually placed only on the left and right edges of the user data, and the pilot signals are transmitted at the edge of the subcarriers used by each user, and the pilot signals are used for channel estimation. Test (refer to the prior art document π]). However, as in the prior art document [2], in a multi-user orthogonal frequency division multiplexing system, the frequency error of each user cannot be perfectly compensated at the same time. When using the pilot signal of [丨] to estimate the channel for the specified user, even if the frequency error is estimated to be perfect, interference will still occur due to the existence of residual frequency errors of other users. Although an empty carrier that does not transmit any information 134182.doc 201029369, such as empty carriers 114, 124, can be added between the user bands, however, mutual interference between users cannot be avoided. Therefore, it is necessary to provide an innovative and progressive multi-user data packet for orthogonal frequency division multiplexing systems to solve the above problems. Prior Technical Literature: [1] Grandmaison M.-E. and Gagnon F, "Channel Estimation Algorithms for Uplink OFDMA Tiles/5 ISWPC, Feb, 2007.

[2] Defeng (David) Huang and Khaled Ben Letaief, 4iAn Interference- Reference Cancellation Scheme for Carrier Frequency Offset Correction in OFDMA System, 5, IEEE Transaction on communications S, VOL.53, NO. 7, July 2005.

[3] Yuping Zhao and Sven-Gustav Haggman, Inter-carrier Interference Self-Cancellation Scheme for OFDM Mobile Communication Systems, IEEE Transaction on communications, VOL. 49, NO. 7, July 2001.

[4] Wee Teck Ng and Vimal K. Dubey, <eAnalysis of PCC-OFDM

Systems for General Time-Varying IEEE Communications leters^ VOL. 9, NO. 5, May 2005. SUMMARY OF THE INVENTION The present invention provides a multi-user data packet for an orthogonal frequency division multiplexing system, which includes: a plurality of users The data packets are arranged according to the user's sorting direction. Each user data packet sequentially has a first group pilot sequence, a user data signal and a second group pilot sequence, and the first group of the i-th user's first pilot sequence and the i-th The second set of pilot sequences of one user overlaps, and the ith uses the 134182.doc 201029369 second group pilot sequence to overlap with the first set of pilot sequences of the i+1th user. Since the pilot sequence of the multi-user data packet of the present invention is transmitted in an overlapping manner, the system bandwidth usage rate is not lowered. In addition, the use of overlapping pilot sequences can reduce the estimation error caused by interference during system channel estimation, and reduce mutual interference between users, resulting in an overall system performance improvement. [Embodiment]

Referring to Figure 2, there is shown a non-intentional use of the multi-user data packet for the orthogonal frequency division multiplexing system of the present invention. The multi-user data packet 20 for the orthogonal frequency division multiplexing system of the present invention comprises: a plurality of user data packets 21, 22, 23. Arranged according to the user's sorting direction (0 to packet), each user data packet sequentially has a first group of pilot sequences, a user data signal and a second group of pilot sequences. The first set of pilot sequences of the i-th user overlaps with the second set of pilot sequences of the second user. The second set of pilot sequences of the i-th user overlaps with the first set of pilot sequences of the magical + user. . In this embodiment, the first group pilot sequence includes three pilot signals, and the second group pilot sequence includes three county signals. The user data packet 21 has a first group of pilot sequences, a first pilot signal 211, a first group of pilot sequences, a second pilot signal 212, a first group of pilot sequences, a third pilot signal 213, and a user data signal. 214, the second group pilot sequence 2 the first pilot signal 215, the second group pilot sequence second pilot signal and the first group pilot sequence third pilot signal 21 7 ^ the i-th user data packet 22 has a The first group of pilot sequences, the first leader I34182.doc 201029369, the flight number 221, the first group of pilot sequences, the second pilot signal 222, the first group of pilot sequences, the third pilot signal 2 2 3, _ user data signal 2 24. A second pilot sequence, a first pilot signal 225, a second pilot sequence, a second pilot signal 226, and a second group of pilot sequences, a third pilot signal 227. The first user data packet 23 has a first pilot sequence, a first pilot signal 231, a first pilot sequence, a second pilot signal 232, a first group of pilot sequences, a third pilot signal, and a user data signal. 9 234, the second pilot flight sequence 235, the second pilot flight second pilot signal 236 and the second pilot flight third pilot signal 237. In this embodiment, the data packet of the i-th user is taken as an example to illustrate that the first piloting signal of the first group of pilots of the i-th user and the first piloting signal of the second group of pilots of the M-th user 215 overlap, the second pilot signal 222 of the first group of pilots of the third user overlaps with the second pilot signal 216 of the φ second group pilot sequence of the Wth user, and the first group of pilots of the i-th user The three pilot signals 223 overlap with the third pilot signal 217 of the second group of the Mth user; the second group of pilot sequences of the user is the first pilot flight 225 and the first group of the i+! users pilots The first pilot signal 231 of the sequence overlaps, the second pilot signal 226 of the second pilot sequence of the i-th user overlaps with the second pilot signal 232 of the first pilot sequence of the i+1th user, the i-th user The third piloting signal 227 of the second group of piloting sequences overlaps with the first group of piloting pilot signals 233 of the i+H solid subscriber. 134182.doc 201029369 Therefore, by using the concept of orthogonal overlap, the pilot signals of adjacent users are overlapped, and the pilot signal design is used to achieve the effect of interference cancellation. And with the orthogonal characteristic concept required for overlapping pilot signals, combined with channel estimation, there is less interference. They are placed in a symmetrical manner so that adjacent users have the same amount of interference. Assume that the adjacent carrier [A > 1 free 1] between the i-th user and the i-th user overlaps the pilot signal V, U is as follows:

V π eU9+Al\eje , eue+^2) τ

ϋ 6ϋθ+Α2) ^eje ^υθ^) (1) where 'ΔΡΔ2 is the phase difference of the rotation and θ is the phase term of the pilot signal. From equation (1), the orthogonal condition can be derived as = y (2). Assuming that the frequency deviation correction for the i-th user at the receiving end is correct, then at the receiving end, the first-scale-1, [and the first +1 carrier The reception signal (8) and <(free + 1) can be expressed as + (^)/(^.,) + eieH^ (^)/(1 + ) + e^(e+4' (k)I(2 + f,..,)], (10))=士[e)Ot) +,W(印(-1 + L ) + ) +,(8)/(1 + &)],

Yi(k + ^ = ^[e;(i+Al)/f(()fc) + e^>Hi_l(k)I(-2 + ) + eieH^(k)I(-l + ) + (^)/(^,,)]. 134182.doc 201029369 where the heart represents the carrier deviation value of the i-th user after the system compensates for the i-th user frequency deviation. exp[Ml-丄)α]· Ν 1 sin (^g) N sm(~a) where /(c〇 represents the parameter expression when the carrier frequency domain deviation is α. In equation (3), each represents the transmission of the second user and the wth user.

The transmission channel is represented in the frequency domain signal. Thus, the pilot of the i-th user is estimated by the pilot signal: H{Q) = \H[Yik-\), Y{kWk + l)^ (4) =Ht{k) + H^{ k)· +1 + eJ<A· A»>] + /(2 + ¢..,) + /(-2 + f..,) '----; L =0 + /(1 + ) 2cos(A,)+ /(-1 +^_j)2cos(A2) * =Hi(k)-\-Zi , where name=/(2+^+/(-2+^)+/( 1+^)2003(^)+/(-1+^^008(^). From equation (4), it can be inferred that 'estimating the interference of the transmission channel under this pilot signal' can be made by appropriate design. The channel estimate has a minimum of interference sources to improve the accuracy of the estimated transmission channel. Therefore, we choose the pilot signal design as follows: V = 1 = 10,000 kg,, kg) U = 1 Γ / (Ύ+& ^ ^τ+θΛ 'VJ ^ , eJ , e 3 where β does not affect the design of equation (5) and can be positioned to any value. 134182.doc -10- (5) 201029369 Therefore, the 'preferred' pilot sequences of the present invention have orthogonal characteristics, and under orthogonal conditions, the phase rotation of the two pilot signals is 120 degrees and 240 degrees. By setting in a symmetrical manner, the multi-user data packet of the present invention not only improves the estimation channel's carrier frequency deviation, but also greatly reduces the estimation accuracy, and can also greatly reduce mutual interference between users. According to the above derivation, the second set of pilot sequences of the i-th user can be derived between the i-th user and the i-i-th user by the same method, and the result is like the pilot signal of the ii user of the formula (5). Applied to the third user, and the n-th user's pilot signal is applied to the i-th user. In this way, the i-th user can obtain the channel estimation results of the used frequency band, and the two results can be used to derive the transmission channel environment of the i-th user transmission data through the first-order linear interpolation operation. The channel model A and the channel model B in Table 1 are simulated. Referring to FIG. 3, the system carrier number is 512, the user sets the number 16, the modulation mode is QPSK, and the channel model is A, and the frequency offset compensation for a specific user carrier is used. Perfect user's and other user-compensated carrier frequency deviations are evenly distributed within ±〇5 and ±〇3, respectively. The multi-user data packet of the present invention and the multi-user data packet of the conventional system are used to estimate the accuracy of the transmission channel. Comparison. Table 1 Parameter Channel Model A Channel Model B Path average power 0dB, -12dB, .15dB OdB, -5dB, -lOdB Path delay Ous, 0.4us, 1.2us ------ Ous, lus, 3us Doppler frequency 0 0 134182.doc 11 201029369

Similar to SUI-2 SUI-3, SUI-5 Referring to Figure 4, the system ^^ modulation mode is QPSK, the channel model is Β'for the specific user load compensation perfect, while the other uses Lugu-grant & + ^ Injury and the average A/main carrier frequency deviation within -3 are = uniform knife cloth, the multi-user data packet of the present invention and the multi-user data packet of the conventional system are compared in estimating the accuracy of the transmission channel .

Referring to FIG. 5, the system carrier number is 512, the user sets the number of modes to QPSK, the channel model is A, and the frequency offset deviation is perfect for a specific user carrier, and the carrier frequency deviations compensated by other users are respectively ±〇_ When the uniform distribution is within 5 and ±0_3, the multi-user data packet of the present invention and the multi-user data packet of the S-head system are compared at the receiving end. · Referring to Figure 6, the number of system carriers is 512, the number of users is set to 16, and the modulation mode is QPSK. The channel model is B. The frequency offset compensation for a specific user carrier is perfect, while the carrier frequency deviations compensated by other users are respectively When the uniform distribution in ±〇·5 and ±〇·3 is performed, the multi-user data packet of the present invention is compared with the multi-user data packet of the conventional system, and the error rate of data demodulation at the receiving end is compared. The above simulation results show that the multi-user data packet of the present invention is better than the conventional system in estimating the accuracy of the transmission channel and the data demodulation error rate at the receiving end. Therefore, since the pilot sequence of the multi-user data packet of the present invention is transmitted in an overlapping manner, the system bandwidth usage rate is not lowered. In addition, by using the overlapping pilot sequence, the estimation error caused by the interference can be reduced in the system channel estimation, and the mutual interference between users can be reduced, so that the overall system performance is improved. The above embodiments are merely illustrative of the principles and effects of the invention and are not intended to limit the invention. Therefore, those skilled in the art can make modifications and changes to the above embodiments without departing from the spirit of the invention. The scope of the invention should be as set forth in the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram showing a multi-user data packet of a conventional orthogonal frequency division multiplexing system. FIG. 2 shows a schematic diagram of a multi-user data packet for an orthogonal frequency division multiplexing system according to the present invention. 3 shows a comparison of the accuracy of the estimated transmission channel of the multi-user data packet of the present invention and the conventional multi-user data packet in the channel model A; FIG. 4 shows the multi-user data packet of the present invention and the conventional multi-user data packet in the channel model. B. Estimated transmission channel accuracy comparison diagram; FIG. 5 is a comparison diagram of data demodulation error rate of the multi-user data packet of the present invention and the conventional multi-user data packet at the receiving end of the channel model A; and FIG. 6 shows the present invention. The data demodulation error rate comparison graph of the user data packet and the conventional multi-user data packet at the receiving end of the channel model A. [Major component symbol description] 10 Traditional orthogonal frequency division multiplexing system multi-user data packet 11 i-th user data packet 111 first pilot signal 112 user data signal 134182.doc -13- 201029369

113 Second pilot signal 12 i-th user data packet 121 first pilot signal 122 user data signal 123 second pilot signal 13 i+ 1 user data packet 131 first pilot signal 132 user data signal 133 second The pilot signal 114 '124 empty carrier 20 The multi-user data packet 21 of the present invention The i-th user data packet 211 The first group pilot sequence first pilot signal 212 The first group pilot sequence second pilot signal 213 first Group pilot sequence third pilot signal 214 user data signal 215 second group pilot sequence first pilot signal 216 second group pilot sequence second pilot signal 217 second group pilot sequence third pilot signal 22 i-th user Data packet 221 The first set of pilot sequences The first pilot signal 222 The first group of pilot sequences The second pilot signal 223 The first group of pilot sequences The third pilot signal 224 User data signal 134182.doc -14 - 201029369 225 226 227 23rd 231rd 232th 233th 234th 235th 236th 237 second group pilot sequence first The second flight pilot sequence of the second flight pilot group, the second pilot flight, the second pilot flight sequence, the third pilot signal, the i-1 user data packet, the first pilot flight sequence, the first pilot signal, the pilot sequence, the second pilot signal, and a group of pilot sequences. Three pilot signal data signals, two groups of pilot sequences, the first pilot signal, the second group, the pilot sequence, the second pilot signal, the second group, the pilot sequence, the third pilot signal, 134182.doc •15·

Claims (1)

201029369 VII. Application for Patent Paradigm··1· A multi-user data packet for orthogonal frequency division multiplexing system, including a plurality of user data packets, arranged according to the user's sorting direction, each user data packet has a sequence-- - a pilot sequence, a user data signal, and a second set of pilot sequences, the first set of pilot sequences of the i-th user overlap with the second set of pilot sequences of the second user, and the second set of pilot sequences of the i-th user The first set of pilot sequences overlaps with the i+1th user. 2. If the request item has multiple user data packets, the first group pilot sequence includes three pilot signals, and the second group pilot sequence includes three pilot signals. 3. In the case of claim 2, the first pilot signal of the first group of pilot sequences overlaps with the first pilot of the second group of pilots. The first pilot signal of the first group of pilots of the i-th user overlaps with the second pilot signal of the second group of pilots of the i-1th user, and the third pilot signal of the first pilot sequence of the first user The third pilot signal of the second group of pilots of the i-th user overlaps with the first pilot sequence of the second pilot sequence of the first user and the first pilot sequence of the i+1th user. The first pilot flight of the second group of pilots of the i-th user overlaps with the second pilot of the first pilot sequence of the third user, and the second pilot of the i-th user The third pilot signal of the sequence overlaps with the third pilot signal of the first group of pilot sequences of the i + H-solid user. 4. The multi-user data packet of request item 2 'the overlapping pilot sequences have orthogonal characteristics. 134182. Doc 201029369 5. As many users of request 4 Expected packet, wherein in the orthogonal condition, the phase rotation term of the two pilot signals of which is 120 degrees and 240 degrees. 134182.doc