Ahmed, B. T., and M. C. Ramon,  "Downlink capacity and interference statistics of wideband code division multiple access microcells for trains in long tunnels",  Communications, IET, vol. 3, no. 4, pp. 603-609, April, 2009.

Ahmed, B. T., M. C. Ramon, and L. H. Ariet,  "Quasi-optimum downlink power control of high altitude platform W-CDMA system",  Vehicular Technology Conference, 2003. VTC 2003-Spring. The 57th IEEE Semiannual, vol. 4, pp. 2476-2479 vol.4, April, 2003.