M.Sc Thesis

M.Sc StudentGabbai Yacov
SubjectAchievable Rates for Partial Feedback Configurations of the
Discrete Memoryless Relay Channel
DepartmentDepartment of Electrical and Computer Engineering
Supervisor DR. Shraga Bross


The work, done by Cover and El-Gamal, on the relay channel considers the achievable rates for the general cases, and determines the capacity in the full feedback scenario where both the relay and the sender observe both channel outputs .

  According to their results general relay channels can roughly be divided into two classes .The first refers to a situation where the relay can decode the sent information better than the receiver does and furthermore, it is capable of forwarding to the receiver the information it wishes to forward thereof. In that case, the relay cooperates with the sender by sending to the receiver some information related to the intended message .

 The second case refers to a situation where the relay-receiver link is rate limited while the capacity of sender-receiver link is larger than that of the sender-relay link. In that case the relay cannot decode the message, yet by sending a compressed version of the data it has observed to the receiver, it can enhance the achievable rate .

This work considers achievable rates for partial feedback configurations of the discrete memoryless relay channel in the aforementioned second regime. Specifically, we consider partial feedback from the receiver to the sender as well as partial feedback from the relay to the sender. It is shown that partial feedback can increase the achievable rate of the general relay channel. This increment is actually a result of the cooperation made possible by the feedback. This additional cooperation becomes important in such cases where the amount of cooperation between the relay and the sender is limited. Such cases are studied for the Gaussian and Z Relay channels .