TABLE OF CONTENTS Transmissions on the physical channels in both reverse and forward directions are structured in frames of fixed length, implying a fixed bit rate for transmission. The information on the transport channels generally occurs in a varying bit rate. Consequently, there is a need to match the two rates for efficient use of the spectrum.
Rate matching in the reverse link channels is achieved by either repeating or puncturing the data. Puncturing is deleting bits before transmission according to a pre-defined scheme. Puncturing is always carried out after channel encoding and, in a sense, it removes some of the redundancies created by the encoder. However, puncturing may weaken the encoding process. On the other hand, it may be required to increase the number of symbols to completely fill in the reverse channel frame through repeating some reverse frame symbols. Clearly, repetition of symbols is preferred since it does not degrade the system channel coding performance.
Similarly, rate matching is required in the forward link and usually the network interrupts the transmission if the rates are not matched. This is called Discontinuous Transmission (DTX).
