Spread spectrum receiver, apparatus and method of a circular buffer for multirate data

#1. Field of the Invention

#The present invention relates to circular buffer, and in particular relates to a method and apparatus of a circular buffer for multi-rate data.

#2. Description of the Related Art

#The invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein:

#FIG. 1 is a block diagram of an exemplary apparatus of receiving multirate data in the invention.

#FIGS. 2a, b and c show exemplary memory allocation incorporated in the circular buffer in FIG. 1.

#The following description is of the best-contemplated mode of carrying out the invention. This description is made for the purpose of illustrating the general principles of the invention and should not be taken in a limiting sense. The scope of the invention is best determined by reference to the appended claims.

#FIG. 1 is a block diagram of an exemplary apparatus of receiving multi-rate data according to the invention, comprising a circular buffer 10 and a controller 12. Circular buffer 10 is coupled to controller 12.

#Circular buffer 10 receives first data Di1 at a first data rate, then second data Di2 at a different second data rate. Controller 12 allocates the buffer space for two consecutive data rates, such that one is partially covered by the other, to meet minimal buffer space requirements of circular buffer 10. The allocated buffer space, or so called a range, could be determined by the Controller 12 according to data write speed, data read speed, the time elapse between the write and the read operations, and the time period of the whole operation. In one embodiment, the data write speed is supposed to be equal to or less than the data read speed. In one embodiment, the time period of the whole operation could be defined as a slot in CDMA system. In particular WCDMA standard, there are 15 slots in a fame of 10 ms, thus the time period of the whole operation is defined as 10/15 ms or 0.667 ms. In one embodiment, the time difference between the write and read operation could be determined as the expected maximum delay between the write and read operation. Ordinary in the skill shall understand the choices of these pre-determined parameters may be considered in various reasons including physical engineering limits. Controller 12 determines a first range in circular buffer 10 based on the first write speed, accesses the first data in the first range, estimates a second range in circular buffer 10 based on the second write speed, and accesses the second data in the second range. The second write speed exceeds the first speed, and more second data Di2 are expected than the first data Di1 in a given period, thus the second range is larger than the first one. Further, the second range is partially covered by the first to reduce minimal capacity requirement of circular buffer 10, which is determined by the maximal second range, subsequently by maximal write speed of the second write speed.