Sidebar: Abbreviations and Acronyms
BN battlefield network
CSI code structure identifier
IM interference management
HDB high delay bandwidth
LT Luby Transform codes
Certain networks, such as ones used for cellular wireless broadcasting, do not have a feedback channel. Applications on these networks still require reliability. Fountain codes in general, and LT codes in particular, get around this problem by adopting an essentially one-way communication protocol.
MANET mobile ad-hoc network
MIMO multiple-input, multiple-output
MMSE minimum mean-squared error
OFDMA orthogonal frequency-division multiple access
OFDMA improves network coverage, since terminals can choose reduced bandwidth transmission to increase their range and reach a distant base station. OFDMA is not available in WI-Fi. (2)
OS opportunistic scheduling
Typically in a wireless system, the signal strength bobs up and down (fades). In WiMAX, we monitor these swings and schedule transmission when the signal is strong. This can improve throughput by about 50%. (2)
PHY physical interface, or transceiver
Rx receiving (reception)
Tx transmitting (transmission)
TR time reversal
In a basic TR communications experiment, the intended receiver first broadcasts a short pilot pulse. The transmitter estimates the channel impulse response and then sends the time reversed version of it back into the channel. The emitted “time reversed” waves back propagate in the channel by retracing their paths and focus in space and time at the source, the intended receiver. (1)
UMB ultra-mobile broadband
WIMAX worldwide interoperability for microwave access
Wi-Fi (also known as 802.11)
works well in offices, cafes, and outdoor “hotspots,” but if you move across town you’ll quickly lose coverage. WiMAX is a wireless data network that can cover an entire city, just like cell phone networks do today. WiMAX (or 802.16) provides speeds comparable to Wi-Fi—between 1 and 10 million bits per second (Mbps) for individual users. So with WiMAX, you have the best of both worlds—mobility and speed. (2)
References:
(1) S. M. Emami, J. Hansen, A. D. Kim, G. Papanicolaou, A. J. Paulraj, D. Cheung, and C. Prettie. Predicted Time Reversal Performance in Wireless Communications Using Channel Measurements, IEEE COMLET, 2002 (Available at ftp://math.stanford.edu/pub/papers/papanicolaou/ComLet.pdf)
(2) Arogyaswami Paulraj. Ask the Expert: What is WiMAX?, 2006. (Available at http://soe.stanford.edu/research/ate_paulraj.html
Source: AHPCRC Bulletin, Vol. 1, Issue 2 (2008)
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