EP0760564A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Random access in multicarrier systems
Assignee: Telia Co AB
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Filing: 1996-07-11
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Granted: —
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Expires: 2016-07-11
Abstract
Abstract Utilisation of frequency divided OFDM (FD OFDM) in the uplink of a multi-access system requires that all mobile stations meet the requirements for orthogonality between sub-carriers in the time and frequency domain. Alternatively, another access technique can be used with OFDM, which can tolerate some relaxation in orthogonality requirements, e.g. code division OFDM (CD OFDM, or COFDM). The use of FD OFDM thus requires a random access technique that does not disturb the orthogonality between sub-carriers. Because time synchronisation is essential if orthogonality is to be preserved between sub-carriers, it is vital that delay difference between a mobile station and a base station be estimated during a random access protocol. In a random access protocol, a mobile station transmits a known signal sequence to a base station. The base station can lock onto the known sequence, detect it and estimate the time delay. According to the present invention, the random access sequence can be repeated cyclically and may comprise a m-sequence, a Gold sequence, or a four phase sequence with good cross-correlation properties, which is modulated onto the sub-carriers in the frequency domain. The random access sequence is transmitted without guard spaces. The random access sequence may be modulated onto all sub-carriers, or alternatively onto selected sub-carriers only. Alternatively, the random access sequence may be modulated onto all sub-carriers, but some sub-carriers may be transmitted at higher power than others.
Inventors
- 👤 Bo ENGSTRÖM
- 👤 Roger Larsson
- 👤 Mattias Wahlqvist
- 👤 Christer Östberg
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-02 19:59
CPC Classifications
H; H04; H04L; H04L27/00; H04L27/26; H04L27/2601; H04L27/2602; H04L27/261; H04L27/2613; H04L27/2647; H04L27/2655; H04L27/2656; H04L5/00; H04L5/003; H04L5/0053; H04W; H04W52/00; H04W52/04; H04W52/30; H04W52/32; H04W52/322; H04W52/38; H04W52/50; H04L5/0001; H04L5/0003; H04L5/0005; H04L5/0007; H04L5/0048; H04W56/00; H04W74/00; H04W74/08
Claims Analysis
Total Claims: 30
Claim 1
Independent Claim
60 words
A random access protocol for use in a multi-access digital radio communications system having a plurality of mobile stations and a plurality of base stations and using OFDM for an uplink between a mobile station and base station in which a mobile station transmits a random access sequence, characterised in that said mobile station cyclically repeats said random access sequence.
Claim 2
Dependent Claim
17 words
A random access protocol as claimed in claim 1, characterised in that said uplink employs FD OFDM.
Claim 3
Dependent Claim
106 words
A random access protocol as claimed in claim 2, characterised in that said mobile station listens for a PICH transmitted by said base station, and after detection of said PICH, said mobile station synchronises to OFDM symbols transmitted by said base station, said mobile station listens to a BCH for a random access sequence and a subcarrier number for an AGCH and then transmits said random access sequence in a random access channel and, after transmission of a plurality of cycles of said random access sequence, said mobile station checks said AGCH to determine whether, or not, said base station has granted said mobile station access.
Claim 4
Dependent Claim
55 words
A random access protocol as claimed in claim 3, characterised in that said random access sequence is transmitted at a power determined by data carried on the AGCH channel and in that if said mobile station is not granted access to said base station, said mobile station retransmits said random access sequence at higher power.
Claim 5
Dependent Claim
94 words
A random access protocol as claimed in either of claims 3, or 4, characterised in that, on detection of said random access sequence, said base station raises a busy flag in said BCH by removing said random access sequence from said BCH, in that said base station transmits timing advance information on the AGCH, in that said mobile station adjusts its timing advance in accordance with said transmitted data, and in that said mobile station transmits another random access with a new random access sequence to verify timing advance adjustment by said mobile station.
Claim 6
Dependent Claim
76 words
A random access protocol as claimed in claim 5, characterised in that, on receipt of said new random access sequence, said base station transmits an acknowledgment on said AGCH together with data informing said mobile station which sub-carriers will be employed for a DICH and DCCH, and in that said mobile station then transmits a randomly selected number which is echoed by the base station, to identify the mobile station, in order to prevent data collisions.
Claim 7
Dependent Claim
20 words
A random access protocol as claimed in any previous claim, characterised in that said random access sequence is a m-sequence.
Claim 8
Dependent Claim
24 words
A random access protocol as claimed in any of claims 1 to 6, characterised in that said random access sequence is a Gold sequence.
Claim 9
Dependent Claim
29 words
A random access protocol as claimed in any of claims 1 to 6, characterised in that said random access sequence is a four phase sequence with good cross-correlation properties.
Claim 10
Dependent Claim
23 words
A random access protocol as claimed in any previous claim, characterised in that said random access sequence is applied to all available sub-carriers.
Claim 11
Dependent Claim
46 words
A random access protocol as claimed in claim 10, characterised in that certain sub-carriers, dedicated to said random access channel, to which said random access sequence is applied, are transmitted at a higher power than other sub-carriers, to which said random access sequence is also applied.
Claim 12
Dependent Claim
32 words
A random access protocol as claimed in any of claims 1 to 9, characterised in that said random access sequence is applied only to certain sub-carriers dedicated to said random access channel.
Claim 13
Dependent Claim
28 words
A random access protocol as claimed in either claims 11, or 12, characterised in that sub-carriers dedicated to said random access channel are unequally spaced from each other.
Claim 14
Dependent Claim
45 words
A random access protocol as claimed in any previous claim characterised in that said random access sequence is cyclically repeated without any guard space between symbols, and in that all other channels bearing modulated data, such as BCH and DICH, include guard spaces between symbols.
Claim 15
Dependent Claim
34 words
A random access protocol as claimed in claim 14, characterised in that said guard spaces have a duration which has an integer relationship to the duration of a symbol in said random access channel.
Claim 16
Dependent Claim
44 words
A random access protocol as claimed in any previous claim, characterised in that a base station responds to a random access sequence transmitted by a mobile station if, and only if, said random access sequence is detected in at least two consecutive data frames.
Claim 17
Dependent Claim
53 words
A mobile radio telecommunications system comprising a plurality of base stations, a plurality of mobile stations and using OFDM for uplinks between mobile stations and base stations, characterised in that said mobile radio telecommunications system is adapted to operate with a random access protocol as claimed in any of claims 1 to 16.
Claim 18
Independent Claim
98 words
A method of measuring performance of a random access sequence, suitable for use with a random access protocol as claimed in any one claims 1 to 16, characterised in that a signal is generated by modulating a random access sequence to be tested onto a plurality of sub-carriers and then subjecting said signal to IFFT processing, introducing a time shift into said signal, subjecting said signal to a multi path model processing to simulate delay spread and doppler shift and passing said signal to a receiver in which said random access sequence is detected and timing advance estimated.
Claim 19
Dependent Claim
28 words
A method as claimed in claim 18, characterised in that noise is injected into said signal, after said signal has been subject to said multi path model processing.
Claim 20
Dependent Claim
15 words
A method as claimed in claim 19, characterised in that said noise is punctuated noise.
Claim 21
Dependent Claim
108 words
Apparatus for measuring performance of a random access sequence, suitable for use with a random access protocol as claimed in any one claims 1 to 16, characterised in that said apparatus includes IFFT means for inverse fourier transform processing of a signal comprising a random access sequence to be tested, said signal modulated onto a plurality of sub-carriers; time shift means for introducing a random time shift, with a uniform distribution over the duration of one symbol, into the signal; modelling means for simulating, on said signal, the effects of delay spread and doppler shift; and receiving means for detecting said random access sequence and estimating timing advance.
Claim 22
Dependent Claim
31 words
Apparatus as claimed in claim 21, characterised in that said apparatus further includes noise generating means for injecting noise into said signal, after said signal has passed through said modelling means.
Claim 23
Dependent Claim
19 words
Apparatus as claimed in claim 22, characterised in that said noise generating means is adapted to generate punctuated noise.
Claim 24
Dependent Claim
340 words
A mobile radio telecommunications system comprising a plurality of base stations and a plurality of mobile stations and using FD OFDM for uplinks between mobile stations and base stations, and employing a random access protocol in which a mobile station transmits a random access sequence, characterised in that: - said mobile station listens for a PICH transmitted by said base station; - after detection of said PICH, said mobile station synchronises to OFDM symbols transmitted by said base station, said mobile station then transmits said random access sequence in a random access channel; - said mobile station listens to a BCH for a random access sequence that is free and a subcarrier number for an AGCH; - after transmission of a plurality of cycles of said random access sequence, said mobile station checks an AGCH to determine whether, or not, said base station has granted said mobile station access; - said random access sequence is transmitted at a power determined by data carried on the AGCH channel; - if said mobile station is not granted access to said base station, said mobile station retransmits said random access sequence at higher power; - on detection of said random access sequence, said base station raises a busy flag in said BCH by removing said random access sequence from said BCH; - said base station transmits timing advance information on the AGCH; - said mobile station adjusts its timing advance in accordance with said transmitted data; - said mobile station transmits another random access with a new random access sequence to verify timing advance adjustment by said mobile station; - on receipt of said new random access sequence, said base station transmits an acknowledgment on said AGCH together with data informing said mobile station which sub-carriers will be employed for a DICH and DCCH; - said mobile station then transmits a randomly selected number which is echoed by the base station to identify the mobile station in order to prevent data collisions; and - said mobile station cyclically repeats said random access sequence.
Claim 25
Dependent Claim
20 words
A mobile radio telecommunications system as claimed in claim 24, characterised in that said random access sequence is a m-sequence.
Claim 26
Dependent Claim
21 words
A mobile radio telecommunications system as claimed in claim 24, characterised in that said random access sequence is a Gold sequence.
Claim 27
Dependent Claim
26 words
A mobile radio telecommunications system as claimed in claim 24, characterised in that said random access sequence is a four phase sequence with good cross-correlation properties.
Claim 28
Dependent Claim
37 words
A mobile radio telecommunications system as claimed in any of claims 24 to 27, characterised in that each of said plurality of mobile stations includes means adapted to apply said random access sequence to all available sub-carriers.
Claim 29
Dependent Claim
57 words
A mobile radio telecommunications system as claimed in claim 28, characterised in that certain sub-carriers are dedicated to said random access channel and in that each mobile station has power control means adapted to cause said certain sub-carriers to be transmitted at a higher power than other sub-carriers, to which said random access sequence is also applied.
Claim 30
Dependent Claim
40 words
A mobile radio telecommunications system as claimed in any of claims 24 to 27, characterised in that each mobile station includes means for applying said random access sequence to only certain sub-carriers, which are dedicated to said random access channel.
References Cited (Backward Citations)
No citation records indexed.
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