Subchannel Allocation in Relay-Enhanced OFDMA Downlink with Imperfect Feedback

Abstract

Abstract-This paper studies the resource allocation for orthogonal frequency division multiple access (OFDMA) in a fixed amplify-and-forward (AF) relay link. We express closed-form average capacity results for the system when frequency allocation is based on limited and imperfect feedback information and multiple antennae are assumed at the relay node (RN) and the user equipment (UE). Feedback strategies based on the best-M method and resource block (RB)-wise one bit quantization are analyzed and compared. Capacity expressions are presented for space-time block coding (STBC) and transmit antenna selection (AS) schemes. The capacity results with imperfect feedback path are of particular interest. The results illustrate that promising tradeoff between the system performance, feedback overhead, and robustness against feedback errors can be achieved by using AS and limited feedback in frequency allocation.

Conventional and modified TAS/OSTBC schemes in dual‐hop fixed‐gain amplify‐and‐forward relaying systems with imperfect feedback

“…They have been included in wireless communications system proposals within 3GPP LTE, WiMax, 4G, HSPA+, and IEEE 802.11n (Wi‐Fi) while also being the promising components of the forthcoming standards. Besides, in order to examine the feasibility of diversity schemes in the real‐world communications applications, and to exhibit the robustness of these schemes to erroneous conditions, researches have been canalized on practical issues such as channel estimation error , feedback delay , feedback error (FE) , spatial correlation , and keyhole effect .…”