M.Sc Thesis

M.Sc StudentCohen Kfir
SubjectBroadcasting over Fading Channels with Mixed Delay
DepartmentDepartment of Electrical and Computer Engineering
Supervisor PROF. Shlomo Shamai )Shitz(


This work considers the problem of transmitting two streams with different delay constraints over a single input single output slow fading flat channel, where only the receiver is aware of the fading realization (treated as channel state information). We consider reliable communications of two data streams, the first is subject to stringent delay constraints (DC) where the transmission must be completed within a single fading block. The other stream is not required to meet any delay demands, and is called the non-delay constrained (NDC) stream, and hence can benefit from the ergodic properties of the channel.

Three novel encoding-decoding strategies are studied, all based on layered communication (the broadcast approach) over the DC stream. That is, as many layers as the channel permits are decoded, resulting in an adjusted DC rate. In the first scheme, the DC treats all of the NDC stream as noise. After many fading blocks, the NDC data stream is decoded suffering from the residual interference of the undecoded DC layers. We derive a closed form solution for the optimal DC layering power distribution, which maximizes the expected sum-rate.

Next, we examine different aspects of cooperation for the different data streams encoders. The second approach is based on ”Writing on Dirty Paper”, where the delay constrained encoder is informed about the other stream’s codeword and uses this knowledge. An analysis about the rate region and comparison to the first scheme is employed. In the third approach, the encoding order is reversed. The DC stream is available progressively (by steps of the fading block length) to the NDC, enabling proper precoding. This model is coined ”Dirty Notes Coding”, where its capacity is introduced, and inner and outer region bounds are given.