Method for rapid synchronization of a point to multipoint communication system
AssigneeAlvarion Ltd.
InventorsMichael Joshua Genossar, Natan Mizrahi, Max Gotman, Naftali Chayat
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Abstract
A modem for more efficiently processing a received analog signal into a digital output. The modem preferably features an adaptive equalizer with coefficients which are saved and reused for processing of subsequent analog signals, in order to reduce the time required to reach convergence. In addition, preferably the modem features an automatic carrier frequency control which adjusts the sampled digital signal according to both the carrier phase offset and the carrier frequency offset. Again, in order to process the signal more quickly and efficiently, preferably the carrier frequency offset is stored and reused for processing subsequent signals.
Claims14
A system for communication between a base station and at least one terminal station, the base station receiving a plurality of sequentially transmitted bursts from the at least one terminal station according to a TDMA (time division multiple access) protocol, each burst featuring a synchronization portion, each of the plurality of sequentially transmitted bursts being denoted Si wherein i is an integer, the plurality of sequentially transmitted bursts including at least a burst Sm and a burst Sn being sent from one terminal station, wherein m and n are each integers and m<n, the system comprising:
- a base station transceiver comprising:
- (i) a receiver unit for receiving the plurality of bursts Si, including at least the burst Sm and the burst Sn, and for producing each of a plurality of analog signals from each of the plurality of bursts Si;
- (ii) an analog-to-digital converter for converting each analog signal to a sampled digital signal, by sampling each analog signal according to a sampling timing;
- (iii) an adaptive equalizer for equalizing each sampled digital signal according to each of a plurality of sets of equalizer coefficients to produce an equalized signal, such that a sampled digital signal corresponding to a particular burst Si is equalized according to a particular set of equalizer coefficients;
- and
- (iv) an equalizer controller for determining each set of coefficients by processing a portion of an equalized signal corresponding to the synchronization portion of a burst Si according to an initialized coefficient adjustment procedure;
- such that for processing a portion of an equalized signal corresponding to the synchronization portion of the burst Sn, said initialized coefficient adjustment procedure is initialized by adapting a set of coefficients at least partially determined by processing a portion of an equalized signal corresponding to the synchronization portion of the burst Sm;
- wherein an equalized signal corresponding to the burst Sn is an Sn-corresponding equalized signal, and said base station transceiver further comprises:
- (v) an automatic carrier frequency control for rotating a phase of said Sn-corresponding equalized signal according to a phase offset of said Sn-corresponding equalized signal to produce a rotated signal, said phase offset being determined according to a carrier frequency offset of said Sn-corresponding equalized signal, said automatic carrier frequency control featuring:
- (A) a loop filter for adapting said carrier frequency offset of said Sn-corresponding equalized signal from a carrier frequency offset determined at least partially from an equalized signal corresponding to the burst Sm;
- and wherein an initial carrier phase is assumed at a start of processing said portion of each equalized signal corresponding to the synchronization portion of each burst Si, said automatic carrier frequency control further featuring:
- (B) a phase initializer for determining a phase error according to said synchronization portion of said Sn-corresponding equalized signal and for correcting said initial carrier phase according to said phase error to determine a correct phase, such that a set of equalizer coefficients being processed according to said synchronization portion corresponding to the burst Sn is also processed according to said correct phase by said initialized coefficient adjustment procedure.
A system for communication between a base station and at least one terminal station, the base station receiving a plurality of sequentially transmitted bursts from the at least one terminal station according to a TDMA (time division multiple access) protocol, each burst featuring a synchronization portion, each of the plurality of sequentially transmitted bursts being denoted Si wherein i is an integer, the plurality of sequentially transmitted bursts including at least a burst Sm and a burst Sn being sent from one terminal station, wherein m and n are each integers and m<n, the system comprising:
- a base station transceiver comprising:
- (i) a receiver unit for receiving the plurality of bursts Si, including at least the burst Sm and the burst Sn, and for producing each of a plurality of analog signals from each of the plurality of bursts Si;
- (ii) an analog-to-digital converter for converting each analog signal to a sampled digital signal, by sampling each analog signal according to a sampling timing;
- (iii) an adaptive equalizer for equalizing each sampled digital signal according to each of a plurality of sets of equalizer coefficients to produce an equalized signal, such that a sampled digital signal corresponding to a particular burst Si is equalized according to a particular set of equalizer coefficients;
- and
- (iv) an equalizer controller for determining each set of coefficients by processing a portion of an equalized signal corresponding to the synchronization portion of a burst Si according to an initialized coefficient adjustment procedure;
- such that for processing a portion of an equalized signal corresponding to the synchronization portion of the burst Sn, said initialized coefficient adjustment procedure is initialized by adapting a set of coefficients at least partially determined by processing a portion of an equalized signal corresponding to the synchronization portion of the burst Sm;
- wherein said base station transceiver further comprises:
- (v) a transmitter for receiving a digital input, for converting said digital input to an analog signal and for transmitting said analog signal to the terminal station, said transmitter featuring a digital-to-analog converter for converting said digital input to produce said analog signal according to a base station transmission clock;
- wherein said sampling timing of said analog-to-digital converter of said base station transceiver is determined directly according to said base station transmission clock;
- and wherein the system further comprises:
- (b) a terminal station transceiver, said terminal station transceiver featuring:
- (i) a receiver unit for receiving said analog signal from the base station;
- (ii) a symbol timing recovery unit for recovering said base station transmission clock from said analog signal to form a recovered clock;
- (iii) an analog-to-digital processing unit for processing said analog signal to a processed digital signal according to said recovered clock;
- and
- (iv) a transmitter for receiving a digital input, for converting said digital input to an analog signal and for transmitting said analog signal to the base station, said transmitter featuring a digital-to-analog converter for converting said digital input to produce said analog signal according to said recovered clock.
A system for communication between a base station and at least one terminal station, the base station receiving a plurality of sequentially transmitted bursts from the at least one terminal station according to a TDMA (time division multiple access) protocol, each burst featuring a synchronization portion, each of the plurality of sequentially transmitted bursts being denoted Si wherein i is an integer, the plurality of sequentially transmitted bursts including at least a burst Sm and a burst Sn being sent from one terminal station, wherein m and n are each integers and m<n, the system comprising:
- a base station transceiver comprising:
- (i) a receiver unit for receiving the plurality of bursts Si, including at least the burst Sm and the burst Sn, and for producing each of a plurality of analog signals from each of the plurality of bursts Si;
- (ii) a digital receiver front-end unit for converting each of said plurality of analog signals to each of a plurality of processed digital signals, a processed signal corresponding to the burst Sn being an Sn-corresponding processed signal;
- and
- (iii) an automatic carrier frequency control for rotating a phase of said Sn-corresponding processed signal according to a phase offset of said Sn-corresponding processed signal to produce a rotated signal, said phase offset being determined according to a carrier frequency offset of said Sn-corresponding processed signal, said automatic carrier frequency control featuring:
- (A) a loop filter for adapting said carrier frequency offset of said Sn-corresponding processed signal from a carrier frequency offset determined at least partially from a processed signal corresponding to the burst Sm;
- wherein an initial carrier phase is assumed at a start of processing said portion of each equalized signal corresponding to the synchronization portion of each burst Si, said automatic carrier frequency control further featuring:
- (B) a phase initializer for determining a phase error according to the synchronization portion of said Sn-corresponding equalized signal and for correcting said initial carrier phase according to said phase error to determine a correct phase, such that a set of equalizer coefficients being processed according to said synchronization portion corresponding to the burst Sn is also processed according to said correct phase by said initialized coefficient adjustment procedure.
A method for communication between a base station and at least one terminal station, the base station receiving a plurality of sequentially transmitted bursts from the at least one terminal station according to a TDMA (time division multiple access) protocol, each burst featuring a synchronization portion, each of the plurality of sequentially transmitted bursts being denoted Si wherein i is an integer, the plurality of sequentially transmitted bursts including at least a burst Sm and a burst Sn being sent from one terminal station, wherein m and n are each integers and m<n, the base station featuring a base station transceiver, the base station transceiver featuring a receiver unit, an analog-to-digital converter, an adaptive equalizer and an equalizer controller, the method comprising the steps of:
- (a) receiving the plurality of bursts Si by the receiver unit, including at least the burst Sm and the burst Sn;
- (b) producing each of a plurality of analog signals from each of the plurality of bursts Si;
- (c) converting each analog signal to a sampled digital signal by the analog-to-digital converter, by sampling each analog signal according to a sampling timing;
- (d) equalizing said sampled digital signal according to said set of equalizer coefficients by the equalizer;
- and
- (e) determining each set of coefficients by the equalizer controller by processing a portion of an equalized signal corresponding to the synchronization portion of a burst Si according to an initialized coefficient adjustment procedure, such that for processing a portion of an equalized signal corresponding to the synchronization portion of the burst Sn, said initialized coefficient adjustment procedure is initialized by adapting a set of coefficients at least partially determined by processing a portion of an equalized signal corresponding to the synchronization portion of the burst Sm;
- wherein the base station transceiver features an automatic carrier frequency control and an equalized signal corresponding to the burst Sn is an Sn-corresponding equalized signal, the method further comprising the steps of:
- (f) determining a carrier frequency offset of said Sn-corresponding equalized signal by said automatic carrier frequency control by adapting said carrier frequency offset of said Sn-corresponding equalized signal from a carrier frequency offset determined at least partially from an equalized signal corresponding to the burst Sm;
- (g) determining a carrier phase offset according to said carrier frequency offset of said Sn-corresponding equalized signal;
- and
- (h) rotating a phase of said Sn-corresponding equalized signal according to said carrier phase offset of said Sn-corresponding equalized signal to produce a rotated signal;
- wherein each burst features a header and a traffic portion, and said header is the synchronization portion, the method further comprising the steps of:
- (i) assuming an initial carrier phase at a start of processing a portion of each equalized signal corresponding to said header of a burst Si;
- (j) determining a phase error according to said portion of said equalized signal corresponding to said header of a burst Si;
- (k) correcting said initial carrier phase according to said phase error to form a correct phase;
- and
- (l) adapting each set of equalizer coefficients according to said correct phase, such that a set of equalizer coefficients employed to equalize a digital sampled signal corresponding to the burst Sn is also processed according to said correct phase by said initialized coefficient adjustment procedure.
The method of claim , wherein the step of processing said analog signal to said processed digital signal by the terminal station transceiver further comprises the step of:
- (i) converting said analog signal to a sampled digital signal by sampling said analog signal according to a terminal station reception clock, said terminal station reception clock being determined directly according to said recovered clock.
Dependencies are inferred from the claim text.