One measurement performance of radios in application like radar, communication, tracking and locating is channel capacity for signalling format and bandwidth provided. Channel capacity is maximum possible theoretical number of bits in 1 second of information which system conveys by means of 1 or more than 1 links in a particular area. As per Shannon-Hartley theorem, channel capacity of proper encoded signals is proportional to channel bandwidth and logarithm of (SNR) signal-to-noise ratio. There is assumption that noise is Additive White Gaussian Noise. Channel capacity linearly increases by increase of bandwidth of channel to most maximum possible value. In fixed channel bandwidths there should be increase in signal powers exponentially. By virtues of inherent large bandwidths in (UWB) Ultra Wide Band Technology, there is achievement of large channel capacities in principle (provided with SNR sufficient). There is no invoking of high-order modulations when requirement of too much high SNR is there. Receiver signal detectors ideally, matches signals transmitted in signal’s shape, time and bandwidth. Mismatches result in margin loss for radio link of (UWB) Ultra Wide Band Technology. Sharing channels with different links (channelization) is difficult issue. It is subject to lots of variables. 2 UWB links share similar spectrum by usage of time hopping orthogonal codes for time modulated pulse position systems or orthogonal codes and orthogonal pulses for fast pulsed base systems.
Forward Error Correction: This is used in (UWB) Ultra Wide Band Technology high data rate pulse systems. This provides channel’s performance by approaching Shannon Limits. OFDM receivers fix typically nearly all errors with low density parity check codes inner codes being followed by few different outer codes. This fixes (the “error floor”) errors occasionally which get past inner code’s LDPC correction being even at lower bit error rates. Example is: Reed -Solomon code with LDPC Coded Modulation (RS-LCM) in turn adds Reed-Solomon Error Correction outer codes. DVB-C2 standard and DVB-T2 standard use BCH code’s outer code. This is done for mopping up residual errors after decoding of LDPC. WiMedia over UWB channels use Hybrid Automatic Repeat Request. Inner error corrections are done by using Reed-Solomon and convolutional coding. Outer error connections are done by using check sequences of frame. When check fails, there is triggering automatically of repeat request (ARQ). When stealth is needed, few UWB formats(pulse-based) is made appearing like slight rises in noise of background for receivers being unaware of complex pattern of signals.
Multipath Interferences: It is distortions of signals as it takes lots of paths to receivers with different polarization shift and different phase shifts. It is problem in technology of narrowband. It affects transmissions of (UWB) Ultra Wide Band Technology. But as per Shannon-Hartley theorem and geometry varieties application to lots of frequencies, abilities of compensation is enhanced. Multipath causes fading. Interference of waves is destructive. Few (UWB) Ultra Wide Band Technology systems have usage of techniques of “rake” receiver for recovering multipath generated copies of pulses original for improving performance of receiver. Different (UWB) Ultra Wide Band Technology systems utilize techniques of channel equalization for achieving similar purposes. Receivers’ narrow-band utilizes same techniques. But they are limited because of various capabilities of resolution of systems of narrowband. Antenna Systems: Multiple-antenna systems: These systems like (MIMO) Multiple-Input-Multiple-Output are used for increasing reception reliability and system throughput. UWB has impulse like response of channel almost. Combinations of techniques of multiple antennas are well preferably.
MIMO coupling spatial multiplexing with high throughput of (UWB) Ultra Wide Band Technology provides possibilities of short ranges network with multi-gigabit rates. Distributed MIMO: For increasing transmission rages, this system and technology exploits antennas distributed amongst various nodes.