Sequence hopping for combinations of pseudo-random noise sequences

#The present invention relates to the field of spread spectrum wireless communications and to any other field that uses Pseudo-random Noise (PN) sequences, such as maximal length code sequences generated using a Linear Feedback Shift Register (LFSR), truncated maximal length code sequences or Gold code sequences.

#Many spread spectrum and other communications systems utilize pseudo-random noise (PN) code sequences for scrambling communications, permitting separation of various transmitting stations, and other purposes. Generally speaking, a PN code sequence exhibits certain random-like properties, even though the code actually is generated in a deterministic manner. Most of the PN code sequences in common use are cyclically repeating sequences of digital 1's and 0's generated using one or more Linear Feedback Shift Registers (LFSRs), such as the maximal length code sequences described below in Section I of the Description of Preferred Embodiments, the truncated maximal length code sequences described below in Section II of the Description of Preferred Embodiments, and the Gold code sequences described below in Section III of the Description of Preferred Embodiments.

#If a device is encoding its transmissions using a PN code sequence, then in order to decode those transmissions, the receiving device requires both the code itself and the proper synchronization with the transmitting device. As a result, once a communications channel is opened between two devices (and, therefore, synchronization has been established), it conventionally has been necessary for each device to continuously generate the PN code sequence, so as to maintain synchronization. It should be noted that such generators often require a high speed clock, such as one that operates at 1.2288 megahertz (MHz). Frequently, such clocks require relatively large power consumption. While this may not be a significant problem for a base station, it can be very significant for a mobile station that operates on battery power.

#The foregoing summary is intended merely to provide a quick understanding of the general nature of the present invention. A more complete understanding of the invention can only be obtained by reference to the following detailed description of the preferred embodiments in connection with the accompanying drawings.

#FIG. 1 is a block diagram of a prime architecture linear feedback shift register.

#FIG. 2 is a block diagram of an insertion architecture linear feedback shift register.

#A. Terminology

#The terminology of this description refers to a “slotted” mode for paging channel monitoring in a DSSS cellular system. The “slot” is the period of time during which the mobile must monitor the paging channel. During any other period of time the mobile does not need to monitor the paging channel. This non-monitoring time is then used for calculations and sleep (i.e., shut down of non-essential components). A low speed clock used in the power saving sleep mode will generally be referred to as a 32 kHz oscillator, although in principle any oscillator could be used. To attain any benefit, the oscillator used should result in lower power drain than retaining the PN sequence generator's normal fast clock. However, it is noted that merely shutting down the PN code sequence generator for some period of time may result in power savings or other advantages. In addition, the present invention may permit the PN code sequence generator to be used to generate other PN code sequences during times when the main PN code sequence is not needed.

#B. Sequence of Events