Ph.D candidate, Department of Electrical Engineering
The University of Texas at Arlington
Arlington, TX 76019
E-mail:
ldd@ieee.org
M.E. : Beijing University of Posts and Telecom, Beijing, China, 2000.
B.E. : Beijing University of Posts and Telecom, Beijing, China, 1997.
With the growing demand of 3G and 4G services, the forward link becomes the bottleneck of the CDMA systems. The high data rate in 3G and 4G CDMA systems, e.g. video service, requires careful and optimal utilization of the base station (BS) power, since the high data rate can easily exhaust the system resource in deep fading. To rise to this new challenge, a new analytical model to characterization the BS power under the power control and soft handoff , which are the key technologies used in CDMA systems, is proposed. Using this new model, we find out that the probability of the outage, which happens when the mobile station (MS) can not maintain reliable communications with the BS, will increase in order to achieve a higher system capacity in the forward link of CDMA systems. The most important results of our new model indicate that whether the soft handoff can increase system capacity or not depends on the properly design of the soft handoff threshold and the limitation of maximum fraction of power allocated by the BS to the MS, which reconciles the arguments in the literature. We further show that power control error can simply increase outage and decrease system capacity. Based on the new model and knowledge obtained there, the optimal power control algorithm is proposed for the multiple BSs in the soft handoff. Comparing to the commonly used power control model in the literature, we show that the proposed optimal power control algorithm can achieve less outage and more system capacity. Recently, a new adaptive video transmission scheme is under research. By jointly shaping the video data rate and the power transmitted from the BS to the MS, this new video transmission scheme can decrease the power requirement from the BS while maintain a certain video quality. To further improve the video quality and achieve a better video rate control, we are researching on the channel estimation and a better algorithm to estimate channel properties, such as the level crossing rate and average fading duration. Further research on how to improve the system capacity and video quality is being extended to CDMA systems including the transmitter diversity, multi-antenna, adaptive coding, and multi-user detection technologies.
. Dongdong Li, V. K. Prabhu, ˇ°Capacity analysis and power control considerations in the future CDMA systemsˇ±, in Texas Systems Day'03
| 1. | Dongdong Li, V. K. Prabhu, "Peformance of Power-control Algorithms in the Forward Link CDMA Systems", to be submitted to ICC'04 |
| 2. | Dongdong Li, J. A. Khoja, V. K. Prabhu, "Outage and Capacity in the Forward Link of a Power-controlled CDMA System",submitted to INFOCOM'04 |
| 3. | Dongdong Li, J. A. Khoja, V. K. Prabhu, "Channel-gain Matched Macrodiversity in the Forward Link of CDMA Systems", to appear in IEEE PIMRC'03 |
| 4. | Dongdong Li, J. A. Khoja, V. K. Prabhu, "System Capacity in the Forward Link of CDMA Systems", to appear in IEEE RAWCON'03 |
| 5. | Jiang Li, Dongdong Li, J.A. Khoja, Q. Liang, M. T. Manry, V. K. Prabhu, "Overcomming Co-channel Interference in TDMA Systems Using SOM Equalizer", to appear in IEEE RAWCON'03 |
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Some of the interesting maxims and jokes: they are always twins.