1,353 research outputs found
Interleaving Channel Estimation and Limited Feedback for Point-to-Point Systems with a Large Number of Transmit Antennas
We introduce and investigate the opportunities of multi-antenna communication
schemes whose training and feedback stages are interleaved and mutually
interacting. Specifically, unlike the traditional schemes where the transmitter
first trains all of its antennas at once and then receives a single feedback
message, we consider a scenario where the transmitter instead trains its
antennas one by one and receives feedback information immediately after
training each one of its antennas. The feedback message may ask the transmitter
to train another antenna; or, it may terminate the feedback/training phase and
provide the quantized codeword (e.g., a beamforming vector) to be utilized for
data transmission. As a specific application, we consider a multiple-input
single-output system with transmit antennas, a short-term power constraint
, and target data rate . We show that for any , the same outage
probability as a system with perfect transmitter and receiver channel state
information can be achieved with a feedback rate of bits per channel
state and via training transmit antennas on average, where and
are independent of , and depend only on and . In addition,
we design variable-rate quantizers for channel coefficients to further minimize
the feedback rate of our scheme.Comment: To appear in IEEE Transactions on Wireless Communication
Channel-based key generation for encrypted body-worn wireless sensor networks
Body-worn sensor networks are important for rescue-workers, medical and many other applications. Sensitive data are often transmitted over such a network, motivating the need for encryption. Body-worn sensor networks are deployed in conditions where the wireless communication channel varies dramatically due to fading and shadowing, which is considered a disadvantage for communication. Interestingly, these channel variations can be employed to extract a common encryption key at both sides of the link. Legitimate users share a unique physical channel and the variations thereof provide data series on both sides of the link, with highly correlated values. An eavesdropper, however, does not share this physical channel and cannot extract the same information when intercepting the signals. This paper documents a practical wearable communication system implementing channel-based key generation, including an implementation and a measurement campaign comprising indoor as well as outdoor measurements. The results provide insight into the performance of channel-based key generation in realistic practical conditions. Employing a process known as key reconciliation, error free keys are generated in all tested scenarios. The key-generation system is computationally simple and therefore compatible with the low-power micro controllers and low-data rate transmissions commonly used in wireless sensor networks
Space-time coding techniques with bit-interleaved coded modulations for MIMO block-fading channels
The space-time bit-interleaved coded modulation (ST-BICM) is an efficient
technique to obtain high diversity and coding gain on a block-fading MIMO
channel. Its maximum-likelihood (ML) performance is computed under ideal
interleaving conditions, which enables a global optimization taking into
account channel coding. Thanks to a diversity upperbound derived from the
Singleton bound, an appropriate choice of the time dimension of the space-time
coding is possible, which maximizes diversity while minimizing complexity.
Based on the analysis, an optimized interleaver and a set of linear precoders,
called dispersive nucleo algebraic (DNA) precoders are proposed. The proposed
precoders have good performance with respect to the state of the art and exist
for any number of transmit antennas and any time dimension. With turbo codes,
they exhibit a frame error rate which does not increase with frame length.Comment: Submitted to IEEE Trans. on Information Theory, Submission: January
2006 - First review: June 200
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