Data integrity is crucial in the provision of a data service. For the CT2 digital cordless system, the 32 kbps duplex channel is exploited to support synchronous and asynchronous data services. The CT2 standard proposed in Europe uses the Reed Solomon (RS) forward error correction (FEC) as the forward error correction technique to achieve data integrity. We investigate the feasibility of the provision wireless asynchronous or synchronous services for in-building data applications and present results of the performance of the (63,k) RS code over the indoor radio channel for the CT2 system.>

A new wide-band HF communication system architecture for a multiple, mobile terminal network has been proposed and analyzed. This architecture embodies the complete removal of high power switching and tuning and achieves control of unwanted radiation by the use of highly linear power amplifiers and adaptive interference cancellation methods. To provide maximum flexibility in system operation, provision is made for transmitting and receiving subsystem assets to be shared among users to the greatest degree possible. The transmitter is simply a power bank into which all exciters are connected, and each receiver has access to a selection of antennas through power dividers, diversity combiners, and adaptive array processors. The implementation of this architecture will permit rapid and flexibile frequency selection and channel configuration to accommodate the complex network relaying strategy that will be necessary in modern warfare environment. Research is being conducted by the U.S. Navy on the technologies that require advancement if this architecture is to be brought to fruition for intratask-force communication. A system engineering analysis, substantial measurements and simulations of adaptive cancellation system performance, and development of critical system components have been conducted to validate the architectural concept.

A number of phenomena that may cause irregularities in extremely low frequency (ELF) ionospheric propagation are suggested. Geomagnetic anisotropy, path asymmetry due to different ionospheric characteristics on the darkened and sunlit hemispheres, effects of strong boundary discontinuities such as the twilight zone or northern latitude sporadicE, and the effects of geophysical trauma such as solar particle fluxes are considered. A primitive analysis of ELF propagation data illustrates that an association can be drawn between the effects of solar charged particle emissions and coincident ELF propagation irregularities. Paths that pass through the auroral zone appear to be most severely affected.

Natural geomagnetic phenomena indicate that wave generation and amplification processes occur spontaneously in the magnetosphere and may be available under certain conditions to permit the frequency band near 1 Hz to be used for communications. An ionospheric duct provides low-loss propagation for waves in this band to distances of thousands of kilometers, and their large skin depth in seawater permits penetration to several hundred meters below the ocean surface. Several methods by which the generation of waves in this band might be possible are described. Methods involving the modulation of ionospheric conductivity include the injection of plasma clouds into the ionosphere and heating of the lowerEregion with powerful radio transmitters. Methods involving nonlinear processes in the magnetosphere include cold plasma injection and very low frequency (VLF)/ultralow frequency (ULF) three-wave interactions.

The ferromagnetic-core type of solenoid that is used as a trailed antenna for communications reception by submarines has not demonstrated adquate sensitivity to satisfy the performance requirements for deeply submerged submarines receiving extremely low frequency (ELF) transmissions from the planned Sanguine communications system. It is possible, however, that a superconducting quantum interference device (SQUID) can be adapted to this role successfully and can permit all requirements of platform depth, speed, and maneuverability to be met. The present status of SQUID's is described, and some laboratory measurements that prove the potential of these devices for the ELF communications reception capability are presented. The engineering development that must be pursued in the areas of 1) sensor and electronics dynamic range, 2) sensor orthogonality, and 3) refrigeration systems to make SQUID ELF sensors available as operational receiving antennas is also discussed.