Improved Differential Space-Time Block codes for Mobile Wireless Systems

BACKGROUND: Space-time block coding (STBC) is used in advanced wireless communications systems to transmit redundant data streams from multiple antennae in order to improve the reliability of data transfer and greatly increase data transmission rates. Such redundancy helps protect wireless data links against fading and other adverse signal distortions caused by scattering, reflection, and refraction in the environment and by thermal noise in the receiver. Differential STBC is a type of STBC that makes signal decoding independent of particular propagation conditions, an important consideration in mobile wireless systems where frequent channel changes and continually changing propagation conditions are the norm. Thus, differential STBC is the focus of much interest for the development of future high data-throughput mobile wireless systems.

At present, the key challenge for differential STBC design is to accomodate relatively simple decoding methods while still being flexible enough to efficiently handle different modulation modes and antenna configurations. In quadrature amplitude modulation (QAM) of signals, for example, one might want to optimize coding gain by altering the set of phase/amplitude points (the “constellation set”) used to digitize signals. Existing differential STBC designs, however, do not offer such constellation set flexibility in conjunction with simple decoding methods.

DESCRIPTION: Researchers have invented a new differential STBC design for multiple antenna transmissions that offers a more attractive trade-off between coding gain and decoding complexity than has been possible with previous designs. The UC design generalizes those of Yuen-Guan-Tjhung (YGT) and Zhu-Jafarkhani (ZJ), combining YGT's more efficient decoding with the ability to work with any constellation set. The block error rates of the UC STBC design are comparable to that of YGT and ZJ (figure 1).

APPLICATIONS: The UC differential STBC design is a strong candidate for use in multiple transmission antenna, high data-throughput mobile wireless systems. As the data transmission rates required for mobile wireless systems steadily increases, especially with the introduction of wireless multimedia/broadband internet services, this invention may become a vital component of such systems.

ADVANTAGES: For a system of four transmitters and a data rate of two bits per Hertz per second, the coding gain of the new UC design is about 1.26 dB better than the YGT code and only 0.50 dB worse than the ZJ code. The UC design shares YGT's lower decoding complexity (4×22b for b bits/dim) as compared to that of ZJ (2×24b). The improvements in STBC efficiency made possible by the UC design may enable lower power consumption in mobile wireless units and better network coverage by multi-antennae transmitters.

REFERENCE: 2006-423

FIGURE 1—Comparison of block decoding error rates for the YGT, ZJ, SP(2), and the proposed UC differential STBC designs for four transmitters and one receiver with 2 bits/Hz/s data rates and a block of four symbols. Error rates for the “clairvoyant” versions of these codes are calculated assuming that the previous block is error-free.

Attached files:
2006-423.jpg

Type of Offer: Licensing



Next Patent »
« More Computer Science Patents
« More Telecommunications Patents

Share on      


CrowdSell Your Patent