We show that the length of a composite channel is regarded up to the whole symbol duration for variable-gain relay (VGR), which generates the received power constant instantaneously. The enlarged channel length causes system burden, which is due to long-channel estimation, i.e., an increase in pilot overhead, a decrease in bandwidth efficiency, and a degradation of system performance. To prevent this effect and minimize the length of the composite channel, phase compensation of the sourcerelay (SR) link channel should be added to the VGR, although this addition increases complexity. A system that adopts VGR with phase compensation performs better and has higher bandwidth efficiency.
Bibliographical noteFunding Information:
Manuscript received April 1, 2009; revised August 21, 2009. Current version published February 19, 2009. This work was supported in part by the Korea Science and Engineering Foundation through the National Research Laboratory Program under Grant R0A-2007-000-20043-0 and in part by the Ministry of Knowledge Economy, Korea, through the Information Technology Research Center support program supervised by the National IT Industry Promotion Agency under Grant NIPA-2009-(C1090-0902-0005). The review of this paper was coordinated by Prof. H. Liu.
All Science Journal Classification (ASJC) codes
- Automotive Engineering
- Aerospace Engineering
- Electrical and Electronic Engineering
- Applied Mathematics