摘要:
A system for the efficient use of CORDIC rotators is provided. The system includes at least one first rotator operating in vector mode and includes a sign storage buffer. The system also includes at least one bit inverter coupled between the first rotator and a second rotator, the second rotator operating in rotation mode.
摘要:
A method is disclosed for PN correlation and symbol synchronization of a spread spectrum signal at a receiver when a symbol boundary of the spread spectrum signal is not on a PN epoch or is otherwise unknown. The method includes the operation of modulating the spread spectrum signal with a PN code to form a potentially despread signal. The potentially despread signal can be integrated for a plurality of symbol times at a rate of N integrations per symbol time to form N symbol energies per symbol for a plurality of symbols. Each of the N symbol energies can correspond to a different symbol time hypothesis. The N symbol energies from the plurality of symbols can be added respectively to form N summed symbol time hypotheses. The Nth summed symbol time hypothesis having maximum power can be found. The Nth summed symbol time hypothesis can relate to a location of the symbol boundary.
摘要:
A system and method for detecting a spread spectrum encoded message within a received signal is described. The spread spectrum encoded message has an unknown code phase, unknown code frequency offset, and unknown carrier frequency offset. A plurality of code phase hypotheses, code frequency offset hypotheses, and carrier frequency offset hypotheses are searched in parallel. The unknown code phase, unknown code frequency offset, and unknown carrier frequency offset may also be estimated.
摘要:
A parallel correlator and method includes temporarily storing in a series of P sequence registers, each of length R1, serial bit-sequences of a code of length N=P*R1. In a first-level of processing, certain unique bit sequences are inverted to reduce the number of unique bit sequences by half. Identical bit-sequences are then combined and temporarily stored in a first-level sub-accumulation register. Alternatively, bit sequences differing by only one bit may be combined in a common first-level sub-accumulation register. Further levels of similar processing may be imposed, where each subsequent level taps and inverts only a portion of the bits in the above level of processing, thereby reducing the number of unique bit sequences. Finally, all negative energy is combined in one register position, inverted, and added to all positive energy in the other register positions. When the spreading code was aligned among the series of sequence registers, the energy is added coherently and an energy peak is output, indicating alignment of the spreading code in the sequence registers.
摘要:
A method is presented for estimating a phase error for first (rI) and second (rQ) orthogonal signal components spread respectively by different first cI and second cQ spreading codes. A cross-despread value IdQ and/or QdI is determined by despreading one signal component with the spreading codes associated with the other signal component (rI with cQ or rQ with cI). In parallel, the same signal component is also despread with its associated spreading code to determine an estimated data symbol for that component. An interference of Q into I or I into Q is calculated and multiplied by the estimated data symbol, and subtracted from the cross-despread value to achieve an estimate of phase error. Preferably, both cross-despread values are obtained, normalized to a common data rate, scaled to maximize signal to noise ratio, and combined into one phase error estimate. A phase error detector includes despreaders, multipliers, and adders to determine the cross-despread value and subtract the interference from it.
摘要:
A communications system employs the use of both synchronous CDMA and FDMA to provide a variable bandwidth waveform with multiple bonded transmitters and receivers that are agile in both frequency and PN code to permit a variable bandwidth and variable rate multiple access system. In a first aspect the teachings provide the use of both CDMA and FDMA together to enable an improved concentration efficiency by making a larger pool of bandwidth available to each user. In a second aspect these teachings enable channel bonding across both code space and frequency space, thus making the system capable of operating within a variable (not necessarily contiguous) bandwidth and at a finely variable rate.
摘要:
Disclosed is a method for transmitting information in a CDMA communication system, the method including steps of (a) multiplexing data and control information into a data stream; (b) encoding the data stream to form a stream of encoded I/Q symbol pairs; (c) inserting synchronization information into the stream of encoded I/Q symbol pairs; and (d) spreading the encoded I/Q symbol pairs and the inserted synchronization information using a same pseudonoise (pn) spreading code prior to transmission as a frame. The preferred frame structure includes an unencoded synchronization field followed by a plurality of multi-byte data fields. Individual ones of the plurality of data fields are separated by a control message field. Individual ones of the control message fields contain a single byte of a multi-byte control message frame.