We use Hurwitz-Radon matrices to construct a space-time code for parallel wireless mobile relays that are located anywhere between a source and a destination. Each relay receives a sequence of ...symbols (i.e., baseband signals corrupted by fading and noise) simultaneously from the source. These symbols are not decoded into information bits at the relays but are rearranged (i.e., space-time modulated) in their orders, amplitudes and phases according to the Hurwitz-Radon code. The relays do not exchange symbols with each other but forward the modified sequences of symbols in parallel to the destination. Our study shows that with R relays, an order of diversity around R/2 can be achieved, i.e., the averaged bit error rate is in the order of 1/SNR/sup R/2/ as opposed to 1/SNR for a single (regenerative) relay system. More than 10 dB power saving, from the baseline of the single relay system, can be achieved with eight (non-regenerative) relays.
Oja's principal subspace algorithm is a well-known and powerful technique for learning and tracking principal information in time series. A thorough investigation of the convergence property of Oja's ...algorithm is undertaken in this paper. The asymptotic convergence rates of the algorithm is discovered. The dependence of the algorithm on its initial weight matrix and the singularity of the data covariance matrix is comprehensively addressed.
A networking perspective of mobile parallel relays Yingbo Hua; Yu Chang; Yan Mei
3rd IEEE Signal Processing Education Workshop. 2004 IEEE 11th Digital Signal Processing Workshop, 2004,
2004
Conference Proceeding
For mobile ad hoc networking, relaying is one of the most fundamental functions. The traditional relaying strategy is serial, where data packets hop from a single node to another, and the nodes ...neighboring a transmitting node or a receiving node are suppressed from transmission to avoid radio interference. We consider a parallel relaying strategy where neighboring nodes may act as parallel relays with space-time modulation. We demonstrate the feasibility of parallel relaying in ad hoc networks by presenting a generic route discovery algorithm for establishing routes of parallel relays. We also formulate a link layer protocol for forwarding packets through parallel relays. We then provide analytical results of packet loss rate and link delay time to highlight some of the potential benefits of parallel relays. With N parallel relays at each link, a diversity factor, N-squared, is achievable. A power saving of 10 dB or more is possible from serial relaying to parallel relaying.
Smart wireless antenna arrays Yingbo Hua; Yan Mei; Yu Chang
2003 IEEE Topical Conference on Wireless Communication Technology,
2003
Conference Proceeding
Summary form only given. The antenna is indispensable in wireless communications. An antenna array is well known for its power in harnessing spatially distributed radio energy for more reliable data ...reception. Current trends in smart antenna technology primarily focus on mobile environments where fast channel fading is predominant in limiting channel capacities. We present a new frontier in signal processing for wireless communications, which we call smart wireless antenna arrays or, more briefly, wireless antennas. Most (if not all) current antennas are wireless on one end but wired on the other. Wired antennas of large apertures are not always convenient for users. Therefore, we have endeavored to develop smarter antennas that have no wires. Our wireless antennas (or virtual antennas) are a number of wireless mobile relays distributed around a destination receiver (or a set of destination receivers). These relays could be embedded in any wireless mobile device. We show a signal processing framework for wireless antennas.
We first provide an overview of some of the latest developments in wireless communications using multiple transmitters and multiple receivers. We point out the importance of SNR control in fast ...random fading environments. For applications where large antenna arrays are not suitable, we introduce the concept of wireless antennas or wireless relays that are distributed between a source and a destination. We propose Hurwitz-Radon space-time code for the wireless relays. Each relay receives a noisy baseband signal simultaneously from the source. The baseband signals (symbols) are not decoded into information bits at the (non-regenerative) relays, but rearranged (i.e., space-time modulated) in their orders, amplitudes and phases according to the Hurwitz-Radon code. The relays do not exchange symbols with each other, but forward the modified sequences of symbols in parallel to the destination. Our study shows that with R relays, a diversity factor around R/2 can be achieved, i.e., the averaged bit error rate is in the order of 1/SNR/sup R/2/ as opposed to 1/SNR for a single (regenerative) relay system. More than 10 dB power saving, from the baseline of a single relay system, is possible with eight relays. Issues such as channel estimation, symbol synchronization, medium access protocols and signal processing hardware are also discussed.
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