ilable to ensure reliable and error free delivery for connection oriented communication. In contrast, con- nectionless communication proceeds without an LLC to LLC connection, when flow or error control are not required. Cyclic Redundancy Check: A cyclic redundancy check is the computa- tion for a block of data of a number, commonly called the checksum, which summarises and represents the content and organisation of bits in the input data block. By re-computing the CRC, the receiving station can detect any change, whether due to random transmission errors or to malicious inter- ception. In a CRC, the input data bits are taken as the coefficients of a poly- nomial. This polynomial is divided by another fixed polynomial and the CRC checksum bits are the coefficients of the remainder polynomial. The fixed divisor polynomial used in CRC-32 is x32 +x 26 + X 23 + 22 + X 16 + 8 7 + 2 +x+ 1, which can be represented in hexadecimal as either 04C11DB7 or EDB88320 depending on the bit-order convention (LSB first or MSB first). dBi: A logarithmic measure of the gain of an antenna relative to an isotropic antenna. dBm: A logarithmic measure of power relative to 1 milliwatt (mW). A power level of P dBm is ten to the power (P/10) milliwatts, SO that 20 dBm is 100 mW. Delay Spread: The delay spread is the variation in arrival time of wireless signals that propagate from a transmitter to a receiver over multiple paths. Inter symbol interference (ISI) will occur if consecutive symbols are transmitted closer together in time than the delay spread. Differential Binary Phase Shift Keying (DBPSK): A variation of the BPSK modulation technique in which a symbol is represented by a change of carrier phase rather than an absolute phase value. Differential Quadrature Phase Shift Keying (DQPSK): A variation of QPSK modulation in which a symbol is represented by a change of phase between two of the 4 QPSK constellation points, rather than the absolute phase value of one point. Digital Subscriber Line: A class of high speed Internet connectio