METHOD AND APPARATUS FOR INITIAL ACQUISITION AND CELL SEARCH FOR AN OFDMA SYSTEM
A method and apparatus is provided for transmitting an orthogonal frequency domain multiple access (OFDMA) signal including a synchronization channel signal transmitted within a localized portion of a bandwidth of the OFDMA signal, the synchronization channel signal having predetermined time domain symmetry within the localized portion of the bandwidth and including information for providing at least partial cell identification information. The synchronization channel signal enables an initial acquisition and cell search method with low computational load which provides OFDMA symbol timing detection and frequency error detection and frame boundary detection and cell specific information detection in an OFDMA system supporting multiple system bandwiths, both synchronized and un-synchronized systems, a large cell index and an OFDMA symbol structure with both short and long cyclic prefix length.
1 . A method for use in a base station in a wireless communication system for producing an orthogonal frequency domain multiple access (OFDMA) signal comprising a plurality of resource blocks that spans a first bandwidth, each of the plurality of resource blocks comprising a plurality of subcarriers, and the base station including a controller, the method comprising the steps of:
the controller mapping a synchronization channel signal onto a first set of subcarriers of a first set of resource blocks of the OFDMA signal, wherein the synchronization channel signal spans a second bandwidth that is smaller than the first bandwidth;
the controller defining a first guard band comprising a second set of subcarriers of the first set of resource blocks, wherein no signal is mapped onto the second set of subcarriers;
the controller defining a second guard band comprising a third set of subcarriers of the first set of resource blocks, wherein no signal is mapped onto the third set of subcarriers, and the first set of subcarriers is between the second and third sets of subcarriers; and
the controller mapping a data signal onto a fourth set of subcarriers of a second set of resource blocks of the OFDMA signal, the fourth set of subcarriers being different from the first, second, and third sets of subcarriers, and the second set of resource blocks being different from the first set of resource blocks.
2 . The method of claim 1 , wherein the synchronization channel signal of the second bandwidth is within a central portion of the first bandwidth.
3 . The method of claim 1 , wherein the synchronization channel signal of the second bandwidth is within a central portion of the first set of resource blocks.
4 . The method of claim 1 , wherein the first, second, and third sets of subcarriers are between first ones of the fourth set of subcarriers and second ones of the fourth set of subcarriers.
5 . The method of claim 1 , further comprising:
the controller defining a third guard band comprising a fifth set of subcarriers, wherein no signal is mapped onto the fifth set of subcarriers; and
the controller defining a fourth guard band comprising a sixth set of subcarriers, wherein no signal is mapped onto the sixth set of subcarriers, and the first, second, third, and fourth sets of subcarriers are between the fifth and sixth sets of subcarriers.
6 . The method of claim 1 , further comprising the base station transmitting the OFDMA signal including the first guard band, the synchronization channel signal, the second guard band, and the data signal.
7 . The method of claim 1 , wherein the base station also includes a synchronization channel signal generator, and the method further comprises:
the synchronization channel signal generator generating the synchronization channel signal comprising at least partial cell identification information associated with the base station.
8 . The method of claim 7 , wherein the at least partial cell identification information comprises cell group identification information identifying a plurality of base stations in the wireless communication system, one of which is the base station.
9 . The method of claim 7 , wherein the at least partial cell identification information comprises unique cell identification information associated with the base station identifying the base station within a group of base stations.
10 . The method of claim 1 , wherein a number of the first set of resource blocks is a largest integer number that defines the second bandwidth as being smaller than a bandwidth spanned by the first set of resource blocks.
11 . The method of claim 7 , wherein the synchronization channel signal comprises a set of synchronization channel signal sequence elements that are derived in response to a modification of a general chirp like (GCL) sequence, wherein the GCL sequence is modified to fit a predetermined channel size of the OFDMA signal and is defined in response to the at least partial cell identification information associated with the base station.
12 . The method of claim 11 , wherein the modification of the GCL sequence comprises deleting one or more sequence elements of the GCL sequence, and
generating the synchronization channel signal comprises the synchronization channel signal generator generating the synchronization channel signal comprising the set of synchronization channel signal sequence elements derived in response to the modification of the GCL sequence.
13 . The method of claim 11 , wherein the set of synchronization channel signal sequence elements are derived in response to the modification of the GCL sequence, and an index of the GCL sequence corresponds to the at least partial cell identification information associated with the base station.
14 . The method of claim 13 , wherein the at least partial cell identification information corresponding to the index of the GCL sequence comprises unique cell identification information associated with the base station identifying the base station within a group of base stations.
15 . The method of claim 7 , wherein the synchronization channel signal comprises a set of synchronization channel signal sequence elements that are based on a cyclically shifted maximal length binary sequence with a cyclic shift of the maximal length binary sequence defined in response to at least partial cell identification information associated with the base station.
16 . The method of claim 15 , wherein the at least partial cell identification information comprises cell group identification information identifying a plurality of base stations in the wireless communication system, wherein one of the plurality of base stations is the base station.
17 . The method of claim 1 , wherein the synchronization channel signal comprises one or more synchronization channel sequence elements, the OFDMA signal comprises a plurality of OFDMA symbol periods, and the plurality of synchronization channel signal sequence elements are distributed over the plurality of subcarriers and more than one of the plurality of OFDMA symbol periods.
18 . The method of claim 1 , wherein the synchronization channel signal further comprises first and second information providing at least a portion of cell specific information.
19 . The method of claim 18 , wherein the synchronization channel signal comprises one or more synchronization channel sequence elements, and the at least a portion of one or both of the first information and the second information is encoded into a plurality of individual elements of the one or more synchronization channel sequence elements.
20 . An orthogonal frequency domain multiple access (OFDMA) base station in a wireless communication system for generating and transmitting an OFDMA signal comprising a plurality of resource blocks that spans a first bandwidth, each of the plurality of resource blocks comprising a plurality of subcarriers, the OFDMA base station comprising:
a synchronization channel generator generating a synchronization channel signal;
a data signal generator generating a data signal;
a controller coupled to the synchronization channel generator and the data signal generator and configured to:
map a synchronization channel signal onto a first set of subcarriers of a first set of resource blocks of the OFDMA signal, wherein the synchronization channel signal spans a second bandwidth that is smaller than the first bandwidth,
define a first guard band comprising a second set of subcarriers of the first set of resource blocks, wherein no signal is mapped onto the second set of subcarriers,
define a second guard band comprising a third set of subcarriers of the first set of resource blocks, wherein no signal is mapped onto the third set of subcarriers, and the first set of subcarriers is between the second and third sets of subcarriers, and
map a data signal onto a fourth set of subcarriers of a second set of resource blocks of the OFDMA signal, the fourth set of subcarriers being different from the first, second, and third sets of subcarriers, and the second set of resource blocks being different from the first set of resource blocks; and
transmitter circuitry coupled to the controller and transmitting the OFDMA signal including the first guard band, the synchronization channel signal, the second guard band, and the data signal.
21 . The OFDMA base station of claim 20 , wherein the synchronization channel signal of the second bandwidth is within a central portion of the first bandwidth.
22 . The OFDMA base station of claim 20 , wherein the synchronization channel signal of the second bandwidth is within a central portion of the first set of resource blocks.
23 . The OFDMA base station of claim 20 , wherein the first, second, and third sets of subcarriers are between first ones of the fourth set of subcarriers and second ones of the fourth set of subcarriers.
24 . The OFDMA base station of claim 20 , wherein the synchronization channel generator generates the synchronization channel signal to comprise at least partial cell identification information associated with the base station.
25 . The OFDMA base station of claim 24 , further comprising:
a storage device coupled to the synchronization channel generator and storing the at least partial cell identification information.
26 . The OFDMA base station of claim 24 , wherein the at least partial cell identification information comprises cell group identification information identifying a plurality of base stations in the wireless communication system, wherein one of the plurality of base stations is the base station.
27 . The OFDMA base station of claim 24 , wherein the synchronization channel signal comprises a set of synchronization channel signal sequence elements that are derived in response to a modification of a general chirp like (GCL) sequence, wherein the GCL sequence is modified to fit a predetermined channel size of the OFDMA signal and is defined in response to the at least partial cell identification information.
28 . The OFDMA base station of claim 24 , wherein the synchronization channel signal comprises a set of synchronization channel signal sequence elements that are based on a cyclically shifted maximal length binary sequence with a cyclic shift of the maximal length binary sequence defined in response to the at least partial cell identification information.
29 . A method for use in a wireless communication receiver for receiving an orthogonal frequency domain multiple access (OFDMA) signal comprising a plurality of resource blocks, the wireless communication receiver including a controller and receiver circuitry, the method comprising the steps of:
receiving, by the receiver circuitry, the OFDMA signal comprising a first guard band, a synchronization channel signal, and a second guard band, wherein the synchronization channel signal is between the first guard band and the second guard band, wherein the first guard band and the second guard band span respective first and second bandwidths of the OFDMA signal, and wherein no signal is transmitted on the first guard band and the second guard band;
the controller detecting at least a portion of a first set of the plurality of resource blocks within the OFDMA signal, wherein the first set of the plurality of resource blocks comprises the synchronization channel signal, and the synchronization channel signal spans a bandwidth less than a bandwidth spanned by the first set of the plurality of resource blocks; and
the controller detecting the synchronization channel signal within the first set of the plurality of resource blocks.
30 . The method of claim 29 , wherein the step of detecting the synchronization channel signal comprises the step of the controller deriving, based on the synchronization channel signal, at least partial cell identification information associated with a base station transmitting the OFDMA signal.
31 . The method of claim 29 , wherein the controller detects multiple occurrences of the synchronization channel signal within the first set of resource blocks, and the method further comprises:
the controller further deriving the synchronization channel signal by averaging the multiple occurrences of the synchronization channel signal.
32 . The method of claim 29 , wherein the synchronization channel signal comprises one or more synchronization channel signal sequence elements, and wherein the step of detecting the synchronization channel signal comprises the step of:
the controller detecting the synchronization channel signal in response to detecting a general chirp like (GCL) sequence of the one or more synchronization channel sequence elements.
33 . The method of claim 32 , wherein the GCL sequence has an index associated therewith, and wherein the step of detecting the synchronization channel signal comprises the step of detecting the synchronization channel signal in response to detecting the index of the GCL sequence.
34 . The method of claim 33 , wherein the step of detecting the synchronization channel signal comprises the step of deriving at least partial cell identification information associated with a base station transmitting the OFDMA signal in response to the index of the GCL sequence.
35 . The method of claim 34 , wherein the step of detecting the synchronization channel signal comprises the step of deriving the at least partial cell identification information comprising unique cell identification information identifying the base station within a group of base stations in response to the index of the GCL sequence.
36 . The method of claim 29 , wherein the synchronization channel signal comprises one or more synchronization channel signal sequence elements, and wherein the step of detecting the synchronization channel signal comprises the step of the controller deriving at least partial cell identification information associated with a base station transmitting the OFDMA signal in response to detecting an amount of cyclic shift of a cyclically shifted maximal length binary m-sequence of the one or more synchronization channel sequence elements.
37 . The method of claim 29 , wherein the synchronization channel signal comprises one or more synchronization channel signal sequence elements, and wherein the step of detecting the synchronization channel signal comprises the step of deriving at least partial cell identification information comprising cell group identification information identifying a cell group comprising one or more base stations including the base station transmitting the OFDMA signal in response to detecting an amount of cyclic shift of a cyclically shifted maximal length binary m-sequence of the one or more synchronization channel sequence elements.
38 . The method of claim 29 , wherein the first set of the plurality of resource blocks further comprises the first guard band, the synchronization channel signal, and the second guard band.
39 . The method of claim 29 , wherein the step of detecting the synchronization channel signal comprises the step of detecting the synchronization channel signal within at least a substantial portion of a center 1.25 MHz of the portion of the OFDMA signal.
40 . The method of claim 29 , further comprising:
the controller detecting at least a portion of a second set of the plurality of resource blocks within the OFDMA signal, wherein a data signal is within the second set of the plurality of resource blocks, and wherein the second set of the plurality of resource blocks is different from the first set of the plurality of resource blocks; and
the controller decoding the data signal from within the second set of the plurality of resource blocks.
41 . A wireless communication receiver for receiving an orthogonal frequency domain multiple access (OFDMA) signal comprising a plurality of resource blocks, the wireless communication receiver comprising:
receiver circuitry receiving the OFDMA signal comprising a first guard band, a synchronization channel signal, and a second guard band, wherein the synchronization channel signal is between the first guard band and the second guard band, wherein the first guard band and the second guard band span respective first and second bandwidths of the OFDMA signal, and wherein no signal is transmitted on the first guard band and the second guard band; and
a controller coupled to the receiver circuitry and detecting at least a portion of a first set of the plurality of resource blocks within the OFDMA signal, wherein the first set of the plurality of resource blocks spans a first bandwidth and comprises the synchronization channel signal, and the synchronization channel signal spans a second bandwidth less than the first bandwidth, the controller further detecting the synchronization channel signal within the first set of the plurality of resource blocks.
42 . The wireless communication receiver of claim 41 , wherein the controller derives at least partial cell identification information in response to the synchronization channel signal, wherein the at least partial cell identification information is associated with a base station transmitting the OFDMA signal.
43 . The wireless communication receiver of claim 41 , wherein:
the controller detects at least a portion of a second set of the plurality of resource blocks within the OFDMA signal, and wherein a data signal is within a bandwidth spanned by the second set of the plurality of resource blocks, and wherein the second set of the plurality of resource blocks is different from the first set of the plurality of resource blocks, the controller further decoding the data signal from within the second set of the plurality of resource blocks.
44 . The wireless communication receiver of claim 41 , wherein the controller detects multiple occurrences of the synchronization channel signal within the first set of the plurality of resource blocks and derives the synchronization channel signal by averaging the multiple occurrences of the synchronization channel signal.
45 . The wireless communication receiver of claim 41 , wherein the synchronization channel signal comprises one or more synchronization channel signal sequence elements, the controller detects a general chirp like (GCL) sequence of the one or more synchronization channel sequence elements, the GCL sequence has an index associated therewith, and the controller detects the synchronization channel signal in response to detecting the index of the GCL sequence.
46 . The wireless communication receiver of claim 45 , wherein the controller derives at least partial cell identification information associated with a base station transmitting the OFDMA signal in response to the index of the GCL sequence.
47 . The wireless communication receiver of claim 46 , wherein the controller derives the at least partial cell identification information comprising unique cell identification information identifying the base station within a group of base stations in response to the index of the GCL sequence.
48 . The wireless communication receiver of claim 41 , wherein the synchronization channel signal comprises one or more synchronization channel signal sequence elements, and wherein the controller derives at least partial cell identification information associated with a base station transmitting the OFDMA signal in response to detecting an amount of cyclic shift of a cyclically shifted maximal length binary m-sequence of the one or more synchronization channel sequence elements.
49 . The wireless communication receiver of claim 41 , wherein the synchronization channel signal comprises one or more synchronization channel signal sequence elements, and wherein the controller derives at least partial cell identification information comprising cell group identification information identifying a cell group comprising one or more base stations including a base station transmitting the OFDMA signal in response to detecting an amount of cyclic shift of a cyclically shifted maximal length binary m-sequence of the one or more synchronization channel sequence elements.
50 . The wireless communication receiver of claim 41 , wherein the first set of the plurality of resource blocks further comprises the first guard band, the synchronization channel signal, and the second guard band.