Soft Handoff and Connection Reliability in

A two-phase soft handoff scheme, which includes an initial power allocation phase followed by a power re- distribution phase, is proposed. The initial power allocation phase makes a handoff decision for each connection by assigning a connection to the BS with the best link quality and allocating a minimum amount of power from the BS for the connection. The initial handoff decisions are made for individual connections independent of other connections or the BS power availability. Therefore, there might be heavily loaded and lightly loaded BSs because (i) traffic load may not be equally distributed in all cells, and (ii) the channel condition of the connections is random. The power re-distribution phase is to smooth out the loading on the system by coordinating the power allocations among neighboring BSs so that more connections can receive reliable transmissions. We then develop an analytical model for studying the connection reliability with the proposed soft handoff scheme. Our results show that the proposed two-phase soft handoff scheme can significantly improve connection reliability and increase system capacity in downlink transmissions.

[1]  Andrew J. Viterbi,et al.  On the capacity of a cellular CDMA system , 1991 .

[2]  W. C. Y. Lee,et al.  Overview of cellular CDMA , 1991 .

[3]  Laurence Mailaender,et al.  Simple inter-cell coordination schemes for a high speed CDMA packet downlink , 2000, VTC2000-Spring. 2000 IEEE 51st Vehicular Technology Conference Proceedings (Cat. No.00CH37026).

[4]  A. Ogawa,et al.  Optimum soft handoff considering non-uniform traffic in CDMA cellular systems , 1999, Gateway to 21st Century Communications Village. VTC 1999-Fall. IEEE VTS 50th Vehicular Technology Conference (Cat. No.99CH36324).

[5]  Xuemin Shen,et al.  Mobility information for resource management in wireless ATM networks , 1999, Comput. Networks.

[6]  Norman C. Beaulieu,et al.  Estimating the distribution of a sum of independent lognormal random variables , 1995, IEEE Trans. Commun..

[7]  Jon W. Mark,et al.  Wireless Communications and Networking , 2002 .

[8]  Michele Zorzi.  Simplified forward-link power control law in cellular CDMA , 1994 .

[9]  Gordon L. Stuber,et al.  Principles of mobile communication (2nd ed.) , 2001 .

[10]  A.-G.A. Daraiseh,et al.  Optimized CDMA forward link power allocation during soft handoff , 1998, VTC '98. 48th IEEE Vehicular Technology Conference. Pathway to Global Wireless Revolution (Cat. No.98CH36151).

[11]  P. Whiting,et al.  Downlink scheduling in CDMA data networks , 1999, Seamless Interconnection for Universal Services. Global Telecommunications Conference. GLOBECOM'99. (Cat. No.99CH37042).

[12]  R. R. Gejji.  Forward-link-power control in CDMA cellular systems , 1992 .

[13]  Teng Joon Lim,et al.  Soft handoffs in CDMA mobile systems , 1997, IEEE Wirel. Commun..

[14]  Seong-Lyun Kim,et al.  Downlink intercell coordination for DS-CDMA non real time data , 2003, The 57th IEEE Semiannual Vehicular Technology Conference, 2003. VTC 2003-Spring..

[15]  Gordon L. Stüber,et al.  CDMA soft handoff analysis in the presence of power control error and shadowing correlation , 2002, IEEE Trans. Wirel. Commun..

[16]  Tong Liu,et al.  Mobility modeling, location tracking, and trajectory prediction in wireless ATM networks , 1998, IEEE J. Sel. Areas Commun..

[17]  Elvino S. Sousa,et al.  An optimum rate/power allocation scheme for downlink in hybrid CDMA/TDMA cellular system , 2000, Vehicular Technology Conference Fall 2000. IEEE VTS Fall VTC2000. 52nd Vehicular Technology Conference (Cat. No.00CH37152).

[18]  James K. Cavers,et al.  Optimizing the downlink power of macrodiversity antennas in an indoor DS-CDMA system , 1999, Gateway to 21st Century Communications Village. VTC 1999-Fall. IEEE VTS 50th Vehicular Technology Conference (Cat. No.99CH36324).

[19]  Laurie Cuthbert,et al.  Optimum size of soft handover zone in power-controlled UMTS downlink systems , 2002 .

[20]  Dongwoo Kim,et al.  A simple algorithm for adjusting cell-site transmitter power in CDMA cellular systems , 1999 .

[21]  Theodore S. Rappaport,et al.  Wireless communications - principles and practice , 1996 .

[22]  Young Hoon Kwon,et al.  Capacity analysis of forward link with deterministic power model in CDMA systems with adaptive antenna array and soft handoff , 2002, Vehicular Technology Conference. IEEE 55th Vehicular Technology Conference. VTC Spring 2002 (Cat. No.02CH37367).