Over the past decades most channel coding schemes have been optimised for achieving the highest possible minimum distance amongst the legitimate codewords, which is an adequate design criterion for the Gaussian channels of wireline based or other quasi- stationary channels. However, the design of channel coding schemes for high error-rate, fading and dispersive wirelesschannels is still in its infancy . Since the radio spectrum is a scarce resource, one of the most important objectives in the design of a digital cel- lular system is the efficient exploitation of the available spectrum in order to accommodate the ever-increasing traffic demands. Trel- lis Coded Modulation (TCM) [46, 4], which is based on combin- ing the functions of coding and modulation, is a bandwidth ef- ficient scheme that has been widely recognized as an excellent error control technique suitable for applications in mobile com- munications. Turbo Trellis Coded Modulation (TTCM) [90, 4] is a more recent channel coding scheme that has a structure similar to that of the family of power efficient binary turbo codes [2, 4], but employs TCM codes as component codes. TCM and TTCM schemes invoked Set-Partitioning (SP) based signal labeling, in or- der to achieve a higher Euclidean distance between the unprotected bits of the constellation. By contrast, parallel trellis transitions are associated with the unprotected data bits, which reduces the decoding complexity. In our TCM and TTCM schemes, random symbol interleavers were utilised for both the turbo interleaver and the channel interleaver.
Our previous work   generalized the multi-hop wireless network coding (MH-WNC) scheme with fixed two transmission time intervals (TTIs) (referred to as 2-TTI MH- WNC) for the L-node K-message MH-TRC. The 2-TTI MH- WNC scheme was proven to markedly improve the spectral efficiency over conventional Non-NC schemes. However, it was also shown that the 2-TTI MH-WNC scheme is unable to outperform Non-NC for all-scale MH-TRCs. The multi- hop analog network coding (MH-ANC) scheme  can only outperform Non-NC in the MH-TRC with a small number of nodes, while the multi-hop compute-and-forward (MH-CPF) scheme  has better outage performance than Non-NC only for the MH-TRC with a large number of nodes.
FEC coding may guarantee the ratio of satisfied users who are receiving the video stream. Afzal et al.  investi- gated the overall system performance when the AL FEC codes are used in video streaming in UMTS and packet radio services. Alexiou et al.  studied the power con- trol of streaming over high-speed downlink packet access systems when the AL FEC is employed. Munaretto et al.  proposed an interesting optimization of the AL FEC coding, video source coding, and the PL rate selection to improve the PSNR of delivered video on cellular networks. The authors in  also considered employing the Raptor codes at the AL to improve the quality of service for video in MBMS in long-term evolution (LTE) networks. They investigated the benefits of the AL FEC to multicast multi- media contents and examined how much FEC redundancy should be used under different packet loss patterns.
Through utilizing the MIMO system this has demonstrated a great improvement on the systems that use a single antenna. One of promising techniques with the appearance of next generation broadband wireless communications is represented by combining the technology of MIMO wireless and the IEEE 802.16m standard (WiMAX) . So, WiMAX adopts the MIMO antenna technique which represents important enhancements in terms of the spectral efficiency and link reliability. Also, the function of the modulation and coding scheme (MCS) can be executed by applying link adaptation based on the ‘got channel’ condition which represents an effective method to improve the execution of the throughput in a cellular system . Hence, a large increase in throughput for the Mobile WiMAX system can be obtained by a combination of the link adaptation method with the MIMO technique. The idea of the AMC is to adapt the modulation and coding scheme (MCS) to the channel conditions to attain the highest spectral efficiency at all times. AMC is the standard approach which has lately been formulated in wireless standards, which include WiMax .
ment). Thus, a large number of layers are discarded, result- ing in statistically higher compression results concerning the file size. However, lossy medical image compression is con- sidered to be unacceptable for performing diagnosis in most of the imaging applications, due to quality degradation that, even minor, can aﬀect the assessment. Therefore, in order to improve the diagnostic value of lossy compressed images, the ROI (region of interest) coding concept is introduced in the proposed application. ROI coding is used to improve the quality in specific regions of interest only by applying lossless or low compression in these regions, maintaining the high compression in regions of noninterest. The wavelet-based ROI coding algorithm implemented in the proposed applica- tion is depicted in Figure 4. An octave decomposition is used which repeatedly divides the lower subband into 4 subbands. Let D denote the number of decomposition level, then the number of subbands M is equal to 4+3(D − 1). Assuming that the ROI shape is given by the client as a binary mask form on the source image, the wavelet coe ﬃ cients on the ROI and on the region of noninterest (RONI) are quantized with di ﬀ er- ent step sizes. For this purpose, a corresponding binary mask is obtained, called WT mask, on the transform domain. The whole coding procedure can be summarized in the following steps.
This dissertation focuses on exploiting WNC in multi-hop two-way relay chan- nels (MH-TRCs). Particularly, a multi-hop wireless network coding (MH-WNC) scheme is designed for the generalized L-node K-message MH-TRC. Theoret- ical studies on the network throughput and performance bounds achieved by the MH-WNC scheme with different relaying strategies (i.e., amplify-and-forward (AF) and compute-and-forward (CPF)) are carried out. Furthermore, by intro- ducing different numbers of transmission time intervals into the MH-WNC, a multiple-time-interval (Multi-TI) MH-WNC is proposed to determine an optimal MH-WNC which can achieve the best outage performance for all-scale MH-TRCs. Finally, this study extends the research on WNC one step forward from two-user networks to multi-user networks. An extended CPF joint with a dominated so- lution for maximizing the overall computation rate is proposed for the multi-way relay channel (mRC) in the last chapter.
In this paper, we propose an opportunistic multicast scheduling scheme that can jointly explore multicast gain, multiuser diversity, and time/frequency diversity in a wireless fading environment. In the proposed scheme, each packet is sent only once to all users in the multicast group at a transmission rate determined by a selected channel gain threshold and an erasure-correction coding is used to deal with possible erasures when the instantaneous signal-to- noise ratio (SNR) of a BS-user link happens to be inadequate. Reed-Solomon (n, k) erasure-correction code is applied to a block of transmitted packets such that erased packets can be recovered as long as the number of erased packets in a block does not exceed the erasure correction capability, that is, (n − k). As each packet can be transmitted in a time or a frequency slot, erasure-correction coding to a block of transmitted packets eﬀectively explores the time/frequency diversity in a wireless fading environment. The selection of channel gain threshold and erasure correction code param- eters are jointly optimized for best multicast throughput. Furthermore, to study the role of channel knowledge, the proposed scheme is considered in two cases: (i) with full channel gain knowledge and (ii) with only partial knowledge of fading type and average SNR. An analytical framework has been developed to evaluate the multicast throughput of the proposed erasure-correction coding opportunistic multicast scheduling (ECOM) scheme as well as the BU and WU approaches. We prove that the e ﬀ ective multicast throughput (i.e., the multicast rate that each user can receive) of WU and BU asymptotically converges to zero as the group size increases while that of our proposed scheme is bounded from zero depending on the SNR. Numerical results illustrate that for small multicast group size, full channel gain knowledge can oﬀer better multicast throughput than partial channel knowledge; however, for large group size, the diﬀerence in multicast rates of these two cases is just negligible. Besides, performance evaluation shows that with the ability of combining both gains, the proposed scheme outperforms both BU and WU for a wide range of SNRs.
We perform an extensive evaluation of CafNC in comparison to five protocols: an adaptive single copy forwarding algorithm (Café ), adaptive multiple-copy forwarding algorithms (CafRep , Retiring Replicants ), a non-adaptive multi-copy forwarding algorithm (Spray and Focus ) and a static network coding algorithm (HubCode ), over multiple criteria using two vastly different connectivity datasets, Infocom 2006  and DieselNet , from the CRAWDAD wireless data archive. The Infocom 2006 dataset  consists of a 4- day long trace that is based on a human mobility experiment conducted at Infocom 2006. A total of 78 volunteers joined the experiment and each was given an iMote device capable of connecting to other Bluetooth- capable devices. In addition 20 static long-range iMote devices were placed at various locations of the conference venue; three of these were semi-static as they were placed in the building lifts. The DieselNet dataset  consists of 20 days of traces of 40 University of Massachusetts transit buses covering approximately 150 square miles. This trace contains connection events between busses as well as between buses and Access Points. DieselNet buses were subject to the schedule of the University of Massachusetts campus. This trace exhibits long periods of disconnections, short periods of connectivity and islands of connectivity that are rarely populated by more than two nodes.
In view of perfect compatibility with the standard source and channel codec, temporal sampling-based multiple description coding (MDC) has become a better choice for practical applications. However, for the frames change from one scene to another temporal correlation may be destroyed by temporal sampling extremely, which results in the false estimation when the related frames are lost at the side decoder. Therefore, in this article the frames containing scene change are detected and duplicated before temporal sampling, which maintains better temporal correlation in each description. Furthermore, for better rate distortion performance temporal sampling is employed adaptively, that is, frame skipping or up-sampling according to the motion characteristics in original video. The experimental results exhibit better performance of the proposed scheme than other schemes whether in the on – off MDC environment or packet lossy network, especially about 15 dB improvements for the frames with scene change. Therefore, it may be a promising choice for video transmission over error-prone channels, especially over wireless networks.
Wireless image transmission has been a very demanding feature in recent multimedia communications. However, a wireless environment is very prone to the fading phenomenon that hears a high error rate channel. The specific application of image transmission over wirelesschannels has deservedly attracted much attention since it requires not only careful design of the coding methodology for the compression of images, but also appropriate selection of the set of channel codes for effective forward error- correction. A variety of error resilient techniques [I, 2] employing product codes based on RCPC/CRC and RS codes for channel protection of other  streams have been recently proposed in the literature. In [41, a scheme based on Turbo-codes was presented which outperformed the method in  for image transmission over wirelesschannels. In  a real-time optimization algorithm was presented for the transmission of independently decodable packet streams over varying channels. The system utilizes the packetization scheme of . In  the system of  was improved by combining the product code scheme of . The methodology in  takes into consideration the dependencies between information in the compressed stream in order to cluster dependent layers and protect them according to their importance.
Network groups appear in practical situations in wireless mesh networks and other systems. A classical example is a bidirectional link where two nodes communicate through a relay. More examples can be found in . In the following, we will assume that all transmissions adopt the network group approach; that is, during each transmission slot, the source node chooses the packets to be combined so that each of the sinks knows all but one of the packets. As a matter of fact, if nodes are close one to each other it is highly probable that many of them overhear the same packets. Nevertheless this assumption is not necessary to obtain NC gain or to apply the technique proposed in this paper. In Section 7, we will extend the results to a more general case, in which a node may not know more than one of the source packets.
destination node, has attracted a lot of attention, due to its ability in expanding the coverage, increasing the capac- ity, and reducing the power consumption. Two-way relay communication is a promising spectral-efficient transmis- sion protocol for it only needs two time slots to complete a process of signal exchange [9, 10]. In such a communi- cation technique, two source nodes exchange signals with the help of relay(s). As a result, there are two traffic flows in a two-way relay transmission (TWRT) process and they are supported by the same physical channels concurrently, which enhances spectral efficiency (SE) .
Recently, some studies regarding the application of adap- tive bit loading algorithms to wirelesschannels appeared [10, 11, 12, 13]. In this case, particular attention must be paid to channel estimation and CSI update rate e ﬀ ects on the performance [14, 15, 16]. However, water-filling-based techniques require a large overhead for CSI feedback, mak- ing them suitable only for static or very slow time varying channels. Moreover, the modem must be able to continually change the modulation format and power on subcarrier ba- sis (high complexity if high data rates are requested). Hence, simple suboptimal algorithms should be investigated in or- der to reduce complexity and CSI overhead.
Since its inception in information theory in 2000, network coding has attracted a significant amount of research attention . After the initial theoretical studies in wired networks, the applicability of network coding for wireless networks was soon identified and investigated extensively . However, wireless links have higher error rates than wired links which are more reliable and predictable, and wireless links vary over short time scales . Moreover, a major distinguishing feature of wireless networks with wired networks is their multi-cast nature [62,63]. Transmissions in wired network do not interfere with each other, while interfer- ence is unavoidable in MACs. Traditionally, channel-access schemes , such as time division multiple access (TDMA) , frequency division multiple access (FDMA) [66, 67], and code division multiple access (CDMA)  are applied to avoid interference.
In addition to the analytical evaluation of throughput, we validate the results in a real-world setup. The hard- ware performance is evaluated using Ettus Research Uni- versal Software Radio Peripherals (USRPs) which are computer-hosted Software Defined Radios (SDRs). The USRPs connect to a host computer via a Gigabit Ethernet link, which the host-based software uses to receive and transmit the baseband IQ stream. The host controls the USRP using USRP Hardware Driver (UHD) commands, including setting parameters such as amplifier gain. The USRP then performs the necessary baseband processing then up/down-conversion and transmission/reception. The Ettus Research N210 USRP is used, which consists of a motherboard and a radio frequency (RF) daughterboard; more details can be found in . In these experiments the XCVR2450 daughterboards are used, these are dual- band transceivers with 100 mW output at 2.4–2.5 GHz and 50 mW output at 4.9–5.85 GHz. In this paper, GNU- Radio , which is an open-source toolkit, is used as the host-processing software.
employed on both layers for forward error correction. The channel coding rates can also be selected adaptively for both the base and enhancement layers based on the channel con- ditions. Then, the two video streams are modulated by using nonuniform MPSK signal constellations where the data from the base layer are mapped to the coarse resolution layer of the signaling constellation while the data from the enhancement layer are mapped to the finer resolution layer of the signal- ing constellation. Finally, the modulated signals are transmit- ted over a wireless link. During transmission, the modulated bitstreams typically undergo degradation due to AWGN, co- channel and/or inter-channel interference and possibly fad- ing, specifically in this paper we model the channel as Ri- cian slow-fading channel. At the receiver side, the received waveforms are demodulated and channel decoded, and then source decoded to form the reconstructed video sequence. The reconstructed sequence may diﬀer from the original se- quence due to both source coding errors and possible chan- nel error e ﬀ ects.
Adaptive filters trained with LMS, NLMS and RLS algorithm initially track variations in Nakagami-m fading channel and perform noise cancellation. A complex, uncorrelated white Gaussian noise with zero mean and unit variance is generated and added to the channels. The adaptive filter operates on the noise corrupted signal and produces an estimate of the noise, which is subtracted from the desired signal. The overall output is used to control the adjustments applied to the tap weights in the adaptive filter. The flowchart shown in figure 6 depicts the above method.
The devised method does not rely on a particular chan- nel coding technique, since it can be applied universally to all block-based FEC schemes. The algorithm itself is also lightweight, as it gives a closed-form expression of the optimal channel code allocation strategy, which can be computed in real time and adaptively respond to changes in the available transmission bandwidth and experienced channel BER. This makes the technique suit- able for channels with unknown and slowly changing error rate and, even, available bandwidth; the video stream receiver should communicate the experienced error rate to the sender side, which in turn would change the UEP solution accordingly. We also show how the algorithm can be practically applied, using JPEG 2000 source coding and R-S channel coding, and present some performance results expressed in terms of either PSNR (peak signal-to- noise ratio) or MSSIM (mean structural similarity index metric).
We have proposed a simple adaptive STBC scheme that always guarantees achieving both full-diversity and full-rate transmis- sion. If the required channel attenuation knowledge is avail- able at the base station equipped with N t transmit antennas and the mobile can afford using N r 0 ≤ N t receive antennas, we can always attain both a full-rate transmission and a diversity gain of order N r 0 × N r 0 along with both coding gain and power gain. Furthermore, the decoder is simple, incurring a low com- plexity. Our future research may consider the employment of various high-rate ASTBC-SVDs, soft-decoded channel codecs and high-order modulation schemes.