Adaptive Video Transmission over Wireless MIMO System

- Adaptive Video Transmission over Wireless MIMO System.
- If the channel state information is perfectly available at the transmitter (Driessen &.
- Burr, 2003), we can maximize the channel capacity to design a realizable video transmission system.
- Under channel capacity limitation, the chapter presents how to employ joint source-channel coding algorithm with adequate modulation techniques to get the possibly best performance in the system design.
- An important matter in designing adaptive video transmission system is how often the feedback of the channel state information should be carried out.
- In fact, the feedback interval is mainly decided by the channel characteristics..
- In our proposed system, we investigate the system performance of a joint MPEG-2 coding scheme with convolutional channel coding and space time block coding (STBC) techniques, associated with suitable modulation method (BPSK or QPSK), for video data transmission over a wireless MIMO system with Rayleigh fading noises.
- Rates assigned to MPEG-2 source code and convolutional channel code as well as space-time block code schemes are based on the feedback information from Performance Control Unit (PCU) under system channel capacity limitation, which ensures the proposed system achieved the best performance compared to a conventional designed system.
- In a conventional way, source coding and channel coding are designed to accomplish the best system performance respectively.
- With simply combining the best source coding scheme with the best channel coding scheme together, the system does not promise a better overall performance..
- Consequently, the present algorithm employs joint source-channel coding scheme and MIMO concept to get the best performance in the system design over fading channel..
- We are interested in the joint source-channel coding with modulation scheme design under the channel capacity constraint consideration in a MIMO system.
- Figure 1 shows joint source-channel codes under the combination of various source coding rates and various channel coding rates.
- Source coding is concerned with the efficient representation of a signal.
- For data, channel coding is necessary to overcome the errors resulted from transmission channel.
- We have noticed that combining source coding with adequate channel coding, we should be able to achieve a better system performance.
- Assuming that the overall system transmission rate r = k/n, where k is the source coding rate and n is the channel coding rate.
- 1, we have found that a better performance (with a lower distortion) can be promised when we increase the source coding rate k, while we increase the channel coding rate n, a higher bit error rate (a lower system performance) happened under the same E b /N 0 , signal-to-noise ratio (SNR) criterion.
- Therefore, we would like to design a transmission system with higher source coding rate k but lower channel coding rate n to achieve a higher overall transmission rate r..
- Since the overall transmission rate r is under channel capacity limitation, we have to justify the concept with proper method to design transmission system..
- Joint source and channel coding with different rates.
- The overall transmission rate r can be obtained by source coding rate k cooperated with channel coding rate n.
- We will not satisfy the system performance while we have a high source compression ratio (lower k) with strong channel protection (lower n).
- It is quite clear that we have to find a better match between source coding rate and channel coding rate to assure an acceptable system performance..
- The most significant criterion in designing a transmission system is the channel capacity limitation.
- The available channel capacity restricts the overall transmission rate r, which is the rate between source coding rate k and channel coding rate n.
- We have to consider source coding rate, channel coding rate, and the corresponding modulation type all together simultaneously to cope with the channel capacity limitation.
- Assuming channel capacity limitation is one bit/transmission, we are asked to keep overall transmission rate r ≤ 1 bit/channel-use, which can be achieved only with k ≤ n.
- The proposed algorithm employs joint source-channel coding scheme with STBC technique to get the best performance in MIMO systems design..
- Experimental results for performance of the overall adaptive video transmission system compared with a conventional scheme over Rayleigh fading channel are shown in Section 3.
- We have applied the integrated transmission system design method (Daut &.
- To transmit a given video bit stream efficiently, we propose a joint source-channel coding system as shown in Figure 2..
- Proposed adaptive video transmission system block diagram.
- In order to reduce the system complexity of decoding, after the source coding stage, we use convolutional code and STBC in channel coding.
- The channel capacity is limited to one bit/transmission..
- 2.1 MPEG2 video source coding.
- The proposed adaptive video transmission system has been experimentally tested using an MPEG2 source coding algorithm provided from MPEG.ORG website..
- The source coding scheme is MPEG2 format and there are 160×120 pixels in every frame.
- It can be seen that the video quality is better with MPEG2 coding rate 0.6659 bit/pixel (bpp) among the three tested coding rates..
- Original captured video Coding rate: 0.4994 bpp.
- Coding rate: 0.3986 bpp Coding rate: 0.6659 bpp.
- Video quality comparison of original and MPEG2 compressed test video frames 2.2 Channel coding – convolutional coding and space-time block coding.
- In order to reduce the channel error effect and to improve the system performance while transmitting video signals over wireless channel, we have employed the convolutional encoder and maximum-likelihood Viterbi hard decision decoder for channel error correction.
- The channel coding rate selected is corresponding to the MPEG2 source coding rate to satisfy the channel capacity limitation to one bit/transmission.
- For the system simulation, we have adopted two modulation types:.
- In order to receive a decent quality video sequence over wireless MIMO system with good coding gain real time, we have selected convolutional code and space time block code (STBC) for the channel coding.
- The advantage with multiple antennas scheme is that it results in a drastic increase in the channel capacity (Foschini &.
- Recursive systematic convolutional (RSC) encoder, coding rate = ½ Type Transmission.
- Channel coding rate, n (Convolutional).
- Source coding rate, k (MPEG2).
- Corresponding source-channel coding rate to achieve transmission rate, r ≈ 1 bit..
- provide any coding gain, therefore, it may need to be combined with an outer channel coding scheme to provide such coding gains.
- We then select convolutional code and space time block code for the channel coding.
- S(2N–1)] T , where N is the number of the subcarriers.
- represents complex conjugate), h 1 ~h 4 are the channel fading coefficients between transmitter antennas and receiver antennas as shown in.
- Assuming that the channel impulse responses can be fully estimated, we then are able to reconstruct ~ 1.
- To realize the channel coding rate effect under wireless Rayleigh fading channel with AWGN noise conditions, we have performed the experiment for 2×2 system antenna structure with three convolutional coding rates: 2/5, 1/2 and 2/3, respectively.
- The resulted system performance is shown in Figure 7.
- The system performance is improved with lower channel coding rate in the experiment.
- On the other side, system with lower channel coding rate (2/5 in this case) resulted in slower overall transmission rate.
- Therefore, if we may alternate the source coding rate corresponding to the channel coding rate, we are able to remain a consistent transmission rate which achieves channel capacity with considerable system BER performance..
- Bit error rate (BER) performance of three concolutional channel coding rates under Rayleigh fading channel with AWGN noise in a 2×2 MIMO system..
- Rates assigned to MPEG2 source coding and convolutional channel coding schemes as well as STBC space diversity selection are based on the feedback information from Performance Control Unit (PCU) under system channel capacity limitation, which ensures the given.
- PCU is the key components in the adaptive system design, where we have assigned three PCU states to report the changeable overall transmission status as shown in Table 3..
- We have set-up three states to collaborate with the variable Rayleigh fading channel conditions..
- 8, H is the output status index of the PCU.
- We have assigned that, H = 0 is the “state A” index, system with good channel condition and a fast channel coding rate (n = 2/3) is assigned.
- index, the channel is in an “OK” condition and the transmission data need more protection (channel coding rate n = 1/2).
- H = –1 is the “state C” index, channel condition has degraded and the channel code with good protection has to be utilized (n = 2/5)..
- System performance analysis.
- Under the channel capacity constraint, which we assumed in the simulation experiment is 1 bit/transmission.
- we have proposed an adaptive MPEG2 video transmission over wireless MIMO system.
- We have also utilized the space diversity with 2×2, 2×1 or 1×2 antenna configurations to obtain an accessible system performance.
- We have adopted three types of rate assignment as shown in Table 1..
- System transmission simulation is based on the system block diagram shown in Fig.
- For the proposed adaptive video transmission system, we have assigned three combinations of the joint source-channel code transmission rate adjusted to be nearly but not greater than 1 bit/transmission (r ≈ 1 and r ≤ 1) associated with proper M-PSK modulation scheme (as listed in Table 1)..
- With appropriate selection of receiver antenna numbers (as shown in Table 3), we have gained space diversity to improve system performance.
- Furthermore, we assumed that the receiver has perfect knowledge of the channel conditions.
- The BER system performance can be improved more with adaptive receiver antenna numbers (as given in Table 2) of the proposed scheme as shown in Figure 11.
- We have extended the total transmitted video frames to 100 for the experiment, each transmission (10 video frames) is added up a 10 bits CTS before transmitted over wireless.
- Rayleigh fading channel.
- From Figure 12, we have noticed that the proposed adaptive coding system with 2 x 2 (fixed antenna numbers) space diversity is outperformed the conventional systems: 2 x 2 STBC coded scheme, 2 x 1 STBC coded scheme, and 1 x 2 maximal ratio receive combining (MRRC) scheme.
- Figure 13 shows the reconstructed video frames of the proposed PCU controlled adaptive system (in Fig.
- In this study, we applied joint source-channel coding with modulation scheme to design an adaptive video transmission over wireless MIMO system.
- The bit rates of MPEG2 video can be adaptive to associate with the convolutional channel codes and space-time block code (STBC) under the channel capacity constraint consideration.
- In order to be consistent with the channel capacity constraint (which is set to be 1 bit/transmission), there are three rate combination types of the joint source-channel coding algorithm as shown in Table 1.
- From the simulation results, we found that the space diversity and the channel code rate both are important factors influenced reconstructed video quality.
- The system performance is also improved with lower channel coding rate in the experiment..
- In this study, the proposed adaptive system can choose an adequate transmission rate and the number of receiver antennas based on the channel condition.
- With the feedback BER.
- Video frame 1 Video frame 2 Video frame 3 Video frame 4.
- Video frame 5 Video frame 6 Video frame 7 Video frame 8.
- Video frame 9 Video frame 10 Video frame 11 Video frame 12.
- Video frame 13 Video frame 14 Video frame 15 Video frame 16.
- Video frame 17 Video frame 18 Video frame 19 Video frame 20.
- Video frame 21 Video frame 22 Video frame 23 Video frame 24.
- Video frame 25 Video frame 26 Video frame 27 Video frame 28.
- Video frame 29 Video frame 30.
- The reconstructed video frames of the proposed PCU controlled adaptive system..
- Performance Bounds for Combined Channel Coding and Space-Time Block Coding with Receive Antenna Selection, IEEE Transactions on Vehicular Technology, Vol