Abstract
Future wireless video transmission systems will consider orthogonal frequency division multiplexing (OFDM) as the basic modulation technique due to its robustness and low complexity implementation in the presence of frequency-selective channels. Recently, adaptive bit loading techniques have been applied to OFDM showing good performance gains in cable transmission systems. In this paper a multilayer bit loading technique, based on the so called "ordered subcarrier selection algorithm," is proposed and applied to a Hiperlan2-like wireless system at 5 GHz for efficient layered multimedia transmission. Different schemes realizing unequal error protection both at coding and modulation levels are compared. The strong impact of this technique in terms of video quality is evaluated for MPEG- video transmission.
Highlights
One of the main goals in the near future of communication systems is the development of multimedia efficient data coding, compression, and transmission techniques that permit real-time mobile communications
This technique is compared with unequal error protection (UEP) realized at channel coding level and with an equal error protection (EEP) scheme based on classic bit loading techniques
The comparison among the different UEP techniques has been performed for MPEG-4 video transmission over wireless systems, in terms of peak signal-to-noise ratio (PSNR)
Summary
One of the main goals in the near future of communication systems is the development of multimedia efficient data coding, compression, and transmission techniques that permit real-time mobile communications. Some recent studies have proposed to perform UEP in the modulation domain, exploiting the characteristics of multicarrier modulations [13, 24] In this case, the fact that a nonuniform bit and power allocation among the subcarriers is required implies a significant modem complexity and a high CSI signaling overhead between the transmitter and the receiver with respect to the uniform case. A simple bit loading algorithm, where the constellation size and power levels are constrained to be uniform for all used subcarriers, is proposed and extended to the multilayer case to perform UEP of layered video sources at the modulation level This technique is compared with UEP realized at channel coding level and with an equal error protection (EEP) scheme based on classic bit loading techniques. The performance evaluation in terms of peak signal-to-noise ratio (PSNR) for MPEG-4 video transmission for wireless data service is addressed, showing the large gain that can be obtained, especially at low SNRs
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