Explain wireless transmission impairments .Ripunjay Tiwari
Ans. Wireless transmission has the following impairments-
(i) Lower security, simple to attack- not only can portable devices be stolen more easily, but the radio interface is also prone to the dangers of eavesdropping. Wireless access must always include encryption, authentication and other security mechanisms which must be efficient and simple to use.
(ii) Low bandwidth- although they are continuously increasing, transmission rates are still very low for wireless devices compared to desktop system. Local wireless systems reach some Mbit/s while wide area systems only offer some 10 Kbit/s. one task would involve adapting applications used with high-bandwidth connections to this new environment so that the user can building. Researchers look for more efficient communication protocols with low overhead.
(iii) Interference- radio transmission cannot be protected against interference using shielding as this is done in coaxial cable or shielded twisted pair. As an instance, electrical and lightning cause severe in interference and result in higher loss rates for transmitted data or higher bit error rates respectively.
(iv) Shared medium- radio access is always realized via a shared medium. Since it is impossible to have a separate wire between a sender and each receiver, different competitiors have to ‘fight’ for the medium. Although different medium access schemes have been developed, several questions are still unanswered as example how to provide quality of service efficiently with different combinations of access, coding, and multiplexing schemes.
(v) Regulations and spectrum- frequencies have to be coordinated, and unfortunately, only a very limited amount of frequencies are available owing to technical and political reasons. One research topic involves determining how to use available frequencies more efficiently, e.g., by new modulation schemes or demand-driven multiplexing. New air interfaces, power aware ad-hoc networks, smart antennas, and software defined radios (SDR) are further improvement. The latter permit for software definable air interfaces but need high computing power.
(vi) High delays, large delay variation – the big variation in ling characteristics is a serious problem for communication protocols used in today’s internet (TCP/IP). In wireless systems, delays of several seconds can takes place, and links can very asymmetrical (i.e., the links offer different service quality depending on the direction to and the wireless device). Applications must be tolerant and use-robust protocols.
(vii) Ad-hoc networking – wireless and mobile computing permits for spontaneous several new questions for research – routing on the networking and application layer, service discovery, network scalability, reliability, and stability etc.