I'm doing my post graduate research on cooperative beamforming too. However, my research is still in infancy stage, so i can't offer much technical support as yet.
Here are some papers on cooperative beamforming that might interest you:
Chuxiang Li1 and Xiaodong Wang,
" Cooperative Multibeamforming in Ad Hoc Networks",
EURASIP Journal on Advances in Signal Processing Volume 2008,
Article ID 310247, 2008
J. N. Laneman, D. N. C. Tse, andG.W.Wornell, “Cooperative
diversity in wireless networks: efficient protocols and outage
behavior,” IEEE Transactions on Information Theory, vol. 50,
no. 12, pp. 3062–3080, 2004.
J. N. Laneman and G. W. Wornell, “Distributed space-timecoded
protocols for exploiting cooperative diversity in wireless
networks,” IEEE Transactions on Information Theory, vol. 49,
no. 10, pp. 2415–2425, 2003.
A. Sendonaris, E. Erkip, and B. Aazhang, “User cooperation
diversity—part I: system description,” IEEE Transactions on
Communications, vol. 51, no. 11, pp. 1927–1938, 2003.
A. Sendonaris, E. Erkip, and B. Aazhang, “User cooperation
diversity—part II: implementation aspects and performance
analysis,” IEEE Transactions on Communications,
vol. 51, no. 11, pp. 1939–1948, 2003.