Pulse or digital communications – Spread spectrum – Frequency hopping
Reexamination Certificate
1998-06-08
2001-06-12
Chin, Stephen (Department: 2734)
Pulse or digital communications
Spread spectrum
Frequency hopping
C375S133000, C370S343000, C370S436000, C455S452200
Reexamination Certificate
active
06246713
ABSTRACT:
BACKGROUND
The present invention relates to air interface design, and more particularly to the use of frequency hopping in a bandwidth-on-demand communications system
In an orthogonal frequency-division multiple access (OFDM) system, the radio band is divided into many narrow orthogonal sub-bands, or channels. In such a system, bandwidth requirements can be tailored to suit each individual user (“bandwidth on demand”) by assigning to each user as many channels as he or she requires.
In an unlicensed band, or in a situation in which channel allocation is uncoordinated, one or more channels may be jammed by other systems or uncoordinated users. One way to reduce the impact of such interference is to use frequency hopping (FH) techniques, where the carrier frequency is changed frequently so as to avoid being jammed continuously. Well-known coding, interleaving and/or retransmission techniques may then successfully be applied to reduce the interference problem.
The combination of OFDM with frequency hopping has the promise of providing bandwidth on demand and jamming resistance. When, however, much of the available bandwidth is allocated to one or only a few users, there are no unused frequencies to hop to. As a consequence, frequency hopping is ineffective under these circumstances. For example, if half of the channels are allocated to one user in a block of channels, there is only one other block to hop to. Similarly, if one fourth of the channels are allocated in a block, there are only three unused blocks of frequencies to choose from for the next hop.
There is therefore a need for techniques that will permit OFDM and other modulation schemes to offer bandwidth-on-demand in combination with effective frequency hopping techniques.
SUMMARY
In accordance with one aspect of the present invention, the foregoing and other objects are achieved in methods and apparatus for operating a radio communication system that utilizes an available frequency spectrum that is divided up into a plurality of channels to be used by the radio communication system. In one embodiment, a number, n, of the channels are allocated to be simultaneously used during a first hop period for communicating with a user of the radio communication system, wherein the allocated channels occupy adjacent frequency bands of the available frequency spectrum, and wherein the number n is greater than one. Then, n of the channels are allocated to be simultaneously used during a second hop period for communicating with the user of the radio communication system. The n channels allocated for use during the second hop period occupy adjacent frequency bands of the available frequency spectrum. Also, at least one of the n channels allocated for use during the second hop period is the same as at least one of the n channels allocated for use during the first hop period; and at least one of the n channels allocated for use during the second hop period is different from all of the channels allocated for use during the first hop period. In this way, non-orthogonal hops are permitted to occur.
In another aspect of the invention, the first and second hop periods may be consecutively occurring hop periods.
In still another aspect of the invention, n of the channels are allocated to be simultaneously used during a third hop period for communicating with the first user of the radio communication system. Here, the n channels allocated for use during the third hop period occupy adjacent frequency bands of the available frequency spectrum; and none of the n channels allocated for use during the third hop period is the same as any of the n channels allocated for use during the first and second hop periods. That is, orthogonal hops are also permitted to occur in the system, with one user sometimes performing non-orthogonal hops, and at other times performing orthogonal hops.
In yet another aspect of the invention, a second number, m, of the channels are allocated to be simultaneously used during the first hop period for communicating with a second user of the radio communication system, wherein the channels allocated for use by the second user occupy adjacent frequency bands of the available frequency spectrum. Then, m of the channels are allocated to be simultaneously used during the second hop period for communicating with the second user of the radio communication system. Here, the m channels allocated for use by the second user during the second hop period occupy adjacent frequency bands of the available frequency spectrum; and the number m is not equal to the number n. Because the number of channels allocated to the different users need not be the same, a frequency on demand system is provided.
In another aspect of the invention, at least one of the m channels allocated for use by the second user during the second hop period is the same as at least one of the m channels allocated for use by the second user during the first hop period; and at least one of the m channels allocated for use by the second user during the second hop period is different from all of the channels allocated for use by the second user during the first hop period. Thus, the second user is also permitted to perform non-orthogonal frequency hopping.
In an alternative embodiment, none of the m channels allocated for use by the second user during the second hop period is the same as any of the m channels allocated for use by the second user during the first hop period. That is, some users may perform an orthogonal hop, while other users perform a non-orthogonal hop.
In yet another aspect of the invention, a metric representative of the quality of a connection is obtained. The metric is then used to adjust the value of the number n (i.e., the number of adjacent channels assigned for concurrent use by the first user). In one embodiment, the metric is a bit error rate. In an alternative embodiment, the metric is a frame error rate. In yet another alternative embodiment, the metric is a carrier-to-interference ratio (C/I).
REFERENCES:
patent: 4850036 (1989-07-01), Smith
patent: 5121408 (1992-06-01), Cai et al.
patent: 5210771 (1993-05-01), Schaeffer et al.
patent: 5263047 (1993-11-01), Kotzin et al.
patent: 5301188 (1994-04-01), Kotzin et al.
patent: 5381443 (1995-01-01), Borth et al.
patent: 5408496 (1995-04-01), Ritz et al.
patent: 5425049 (1995-06-01), Dent
patent: 5442660 (1995-08-01), Kuo et al.
patent: 5459759 (1995-10-01), Schilling
patent: 5483550 (1996-01-01), Hulbert
patent: 5502722 (1996-03-01), Fulghum
patent: 5528622 (1996-06-01), Cadd et al.
patent: 5537434 (1996-07-01), Persson et al.
patent: 5541954 (1996-07-01), Emi
patent: 5701584 (1997-12-01), Dupuy
patent: 5859841 (1999-01-01), Gitlits
patent: 5946624 (1999-08-01), Petranovich et al.
patent: 5999818 (1999-12-01), Gilbert et al.
patent: 6009332 (1999-12-01), Haartsen
patent: 6112094 (2000-08-01), Dent
patent: 0786890A2 (1997-07-01), None
patent: 0825741A2 (1998-02-01), None
Burns Doane Swecker & Mathis L.L.P.
Chin Stephen
Ha Dac V.
Telefonaktiebolaget LM Ericsson (publ)
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