US 6,961,364 B1 · Base station identification in orthogonal frequency division multiplexing based spread spectrum multiple access systems

Abstract

A base station having the strongest downlink signal is identified by utilizing a unique slope of a pilot tone hopping sequence being transmitted by a base station. Specifically, base station identification is realized by determining the slope of the strongest received pilot signal, i.e., the received pilot signal having the maximum energy. In an embodiment of the invention, the pilot tone hopping sequence is based on a Latin Squares sequence. With a Latin Squares based pilot tone hopping sequence, all a mobile user unit needs is to locate the frequency of the pilot tones at one time because the pilot tone locations at subsequent times can be determined from the slope of the Latin Squares pilot tone hopping sequence. The slope and initial frequency shift of the pilot tone hopping sequence with the strongest received power is determined by employing a unique maximum energy detector.

Claims52

Dependent claims

Apparatus for use in a mobile user unit in an orthogonal frequency division multiplexing (OFDM) based spread spectrum multiple access wireless system including at least two adjacent base stations, each one of the adjacent base stations transmitting pilot tones according to one of a plurality of different pilot tone hopping sequences over at least a portion of a pilot sequence transmission time period, said portion including multiple symbol time periods, at least one of the different pilot tone hopping sequences including at least two pilot tones per symbol time period which are separated from one another by at least one tone during said portion of said pilot sequence transmission time period, in each of the different pilot tone hopping sequences the number of pilot tones used in each successive symbol time periods in said portion of said pilot sequence transmission period being the same but the tones used in a symbol time period by any one of the different pilot tone hopping sequences changing in frequency from one symbol time period to the next symbol time period by a frequency shift corresponding to a fixed number of tones, adjacent base stations using different frequency shifts to generate pilot tone hopping sequences with different pilot tone slopes which can be determined from the frequency shift of the pilot tones used in consecutive symbol time periods, the apparatus comprising:

a receiver for receiving one or more of said plurality of different pilot tone hopping sequences having different pilot tone slopes;
and
a detector, responsive to said one or more received pilot tone hopping sequences, said detector including an energy accumulator for generating an accumulated energy measurement for each individual one of the plurality of pilot tone hoping sequences having different slopes over a period including multiple symbol time periods, said detector detecting a received pilot tone hopping sequence having the maximum accumulated energy over said period including multiple symbol time periods.

Apparatus for use in a mobile user unit in an orthogonal frequency division multiplexing (OFDM) based spread spectrum multiple access wireless system comprising:

a receiver for receiving one or more pilot tone hopping sequences each including pilot tones, said pilot tones each being generated at a prescribed frequency and time instants in a prescribed time-frequency grid;
and
a maximum energy detector, responsive to said one or more received pilot tone hopping sequences, for detecting the received pilot tone hopping sequence having the strongest power,
said maximum energy detector including a slope-shift accumulator for accumulating energy along each possible slope and initial frequency shift of said one or more received pilot tone hopping sequences and generating an accumulated energy signal, a frequency shift accumulator supplied with said accumulated energy signal for accumulating energy along pilot frequency shifts of said one or more received pilot tone hopping sequences, and a maximum detector supplied with an output from said frequency shift accumulator for estimating a slope and initial frequency shift of the strongest received pilot tone hopping sequence as a slope and initial frequency shift corresponding to the strongest accumulated energy.

1 more element

A method for use in a mobile user unit in an orthogonal frequency division multiplexing (OFDM) based spread spectrum multiple access wireless system including at least two adjacent base stations, each one of the adjacent base stations transmitting pilot tones according to one of a plurality of different pilot tone hopping sequences, in each of the different pilot tone hopping sequences over at least a portion of a pilot sequence transmission time period, said portion including multiple symbol time periods, the number of pilot tones used in each successive symbol time period in said portion of said pilot sequence transmission time period being the same but the tones used in a symbol time period by any one of the different pilot tone hopping sequences changing in frequency from one symbol time period to the next symbol time period by a frequency shift corresponding to a fixed number of tones, adjacent base stations using different frequency shifts to generate pilot tone hoping sequences with different pilot tone slopes which can be determined from the frequency shift of the pilot tones used in consecutive symbol time periods, the method comprising the steps of:

receiving one or more of said plurality of different pilot tone hopping sequences having different pilot tone hopping slopes;
and
in response to said one or more received pilot tone hopping sequences:
generating an accumulated energy measurement for each individual one of the plurality of pilot tone hoping sequences having different pilot tone hopping slopes over a period including multiple symbol time periods;
and
detecting a received pilot tone hopping sequence having the maximum accumulated energy over said period including multiple symbol time periods.

3 more elements

A method for use in a mobile user unit in an orthogonal frequency division multiplexing (OFDM) based spread spectrum multiple access wireless system comprising the steps of:

receiving one or more pilot tone hopping sequences each including pilot tones, said pilot tones each being generated at a prescribed frequency and time instants in a prescribed time-frequency grid;
and
in response to said one or more received pilot tone hopping sequences, detecting the received pilot tone hopping sequence having the maximum energy, said step of detecting said maximum energy including the steps of accumulating energy along each possible slope and initial frequency shift of said one or more received pilot tone hopping sequences and generating an accumulated energy signal, in response to said accumulated energy signal, accumulating energy along pilot frequency shifts of said one or more received pilot tone hopping sequences, and in response to an output from said step of frequency shift accumulating, estimating a slope and initial frequency shift of the strongest received pilot tone hopping sequence as a slope and initial frequency shift corresponding to the strongest accumulated energy.

Apparatus for use in a mobile user unit in an orthogonal frequency division multiplexing (OFDM) based spread spectrum multiple access wireless system including at least two adjacent base stations, each one of the adjacent base stations transmitting pilot tones according to one of a plurality of different pilot tone hopping sequences over at least a portion of a pilot sequence transmission time period, said portion including multiple symbol time periods, at least one of the different pilot tone hopping sequences including at least two pilot tones per symbol time period which are separated from one another by at least one tone during said portion of said pilot sequence transmission time period, in each of the different pilot tone hopping sequences the number of pilot tones used in each successive symbol time period in said portion of said pilot sequence transmission time period being the same but the tones used in a symbol time period by any one of the different pilot tone hopping sequences changing in frequency from one symbol time period to the next symbol time period by a frequency shift corresponding to a fixed number of tones, adjacent base stations using different frequency shifts to generate pilot tone hopping sequences with different pilot tone slopes which can be determined from the frequency shift of the pilot tones used in consecutive symbol time periods, the apparatus comprising:

means for receiving one or more of said different pilot tone hopping sequences each including pilot tones;
and
means, responsive to said one or more received pilot tone hopping sequences, for generating an accumulated energy measurement for each individual one of the plurality of different pilot tone hoping sequences having different pilot tone slopes;
and
detector means for detecting a received pilot tone hopping sequence having the maximum accumulated energy over a period including multiple symbol time periods.

2 more elements

Apparatus for use in a mobile user unit in an orthogonal frequency division multiplexing (OFDM) based spread spectrum multiple access wireless system comprising the steps of:

means for receiving one or more pilot tone hopping sequences each including pilot tones, said pilot tones each being generated at a prescribed frequency and time instants in a prescribed time-frequency grid;
and
means, responsive to said one or more received pilot tone hopping sequences, for detecting the received pilot tone hopping sequence having maximum energy, said means for detecting said maximum energy including means for accumulating energy along each possible slope and initial frequency shift of said one or more received pilot tone hopping sequences, means for generating an accumulated energy signal, means, responsive to said accumulated energy signal, for accumulating energy along pilot frequency shifts of said one or more received pilot tone hopping sequences, and means, responsive to an output from said means for frequency shift accumulating, for estimating a slope and an initial frequency shift of the strongest received pilot tone hopping sequence as the slope and the initial frequency shift corresponding to the strongest accumulated energy.

Dependencies are inferred from the claim text.

Base station identification in orthogonal frequency division multiplexing based spread spectrum multiple access systems

Life of this patent

Base station identification in orthogonal frequency division multiplexing based spread spectrum multiple access systems

Life of this patent

Abstract

Claims52