Communication method in an FH-OFDM cellular system

• US 20050147024A1
• Filed: 10/22/2004
• Published: 07/07/2005
• Est. Priority Date: 10/29/2003
• Status: Abandoned Application

• Current Assignee: Korea Advanced Institute of Science and Technology, Samsung Electronics Co. Ltd.
• Original Assignee: Korea Advanced Institute of Science and Technology, Samsung Electronics Co. Ltd.
• Inventors: Jung, Young-Ho, Nam, Seung-Hoon, Lee, Yong-Hoon, Kim, Eung-Sun, Hwang, Chan-Soo, Lee, Jong-Hyeuk, Chung, Jae-Hak, Kim, Young-Doo
• Application Number:
  US10/972,034
• Publication Number:
  US 20050147024A1
• Time in Patent Office: Days
• US Class Current: 370/203
• CPC Class Codes: H04B 1/713 using frequency hopping
• CPC Class Codes: H04L 25/0226 sounding signals per se
• CPC Class Codes: H04L 27/2655 Synchronisation arrangements
• CPC Class Codes: H04L 5/0007 the frequencies being orthogonal, e.g. OFDM(A), DMT
• CPC Class Codes: H04L 5/0048 Allocation of pilot signals, i.e. of signals known to the receiver

Abstract

A communication method in an FH-OFDM communication system having a plurality of BSs is provided. A predetermined number of pilot pattern groups are generated, each pilot pattern group having a predetermined number of different pilot patterns for pilot transmission. The pilot patterns in each of the pilot pattern groups are mapped to different FH sequence sets. The pilot patterns and FH sequence sets are assigned to the BSs so that MSs within the service areas of the BSs can identify the BSs.

Claims

1. A communication method in a frequency hopping-orthogonal frequency division multiplexing (FH-OFDM) communication system including a plurality of base stations (BSs), comprising the steps of:

generating a predetermined number of pilot pattern groups, each having a predetermined number of different pilot patterns for pilot transmission;

mapping the pilot patterns in each of the pilot pattern groups to different FH sequence sets; and

assigning the pilot patterns and the FH sequence sets to the BSs so that mobile stations (MSs) within service areas of the plurality of BSs can identify the BSs.

2. The communication method of claim 1, wherein the step of generating the predetermined number of the pilot pattern groups comprises the step of assigning pilots to ((p−

1)M+m)^th sub-carriers for an m^th pilot pattern group, p being a natural number increasing to N_P, starting from 1, and N_P being a number of sub-carriers to which pilots are assigned.

3. The communication method of claim 1, wherein the step of mapping the pilot patterns comprises the step of mapping the pilot patterns such that each of the pilot patterns is a sequence of all 1'"'"'s in every odd symbol time and is a codeword having a largest minimum Hamming distance among (N_P, log₂N_PP) binary block codes in every even symbol time.

4. The communication method of claim 1, wherein the step of mapping the pilot patterns comprises the step of mapping the pilot patterns such that each of the pilot patterns is a sequence of all 1'"'"'s in every odd symbol time and is a Hadamard sequence as long as a number of the pilot patterns included in each of the pilot pattern groups in every even symbol time.

5. The communication method of claim 1, wherein the step of assigning the pilot patterns and the FH sequence sets to the BSs comprises the step of assigning the pilot patterns so that neighbor BSs have pilot patterns in different pilot pattern groups.

6. The communication method of claim 1, wherein the step of assigning the pilot patterns and the FH sequence sets to the BSs comprises the step of assigning the pilot patterns so that neighbor BSs have a same pilot pattern.

7. The communication method of claim 1, further comprising the step of transmitting from each of the BSs a pilot sequence corresponding to a pilot pattern assigned to the BS on sub-carriers corresponding to a pilot pattern group assigned to the BS.

8. The communication method of claim 1, further comprising the steps of:

generating a time-domain preamble from each of the BSs so that energy exists only on sub-carriers corresponding to the pilot pattern group assigned to the BS; and

transmitting from the BS the preamble at a start point of each frame.

9. The communication method of claim 8, wherein the step of generating the time-domain preamble comprises the step of repeating a predetermined real-number sequence as many times as a number of the pilot pattern groups and multiplying an n^th sample among N samples of the time-domain preamble by e^j2π

mn/N, where m is an index of the pilot pattern group assigned to the BS, N is a number of the samples, and n is a sample index (n=1,2, . . . N).

10. An access method in a mobile station (MS) in a frequency hopping-orthogonal frequency division multiplexing (FH-OFDM) communication system including a plurality of base stations (BSs), comprising the steps of:

receiving a plurality of symbols from a BS, each having pilot samples;

detecting sub-carriers that deliver the pilot samples in each of the symbols;

identifying a pilot pattern group corresponding to the pilot sub-carriers;

detecting a pattern of the pilot samples; and

estimating an FH sequence set corresponding to the pilot pattern to receive data from the BS.

11. The access method of claim 10, wherein the step of identifying a pilot pattern group corresponding to the pilot sub-carriers comprises the step of detecting a pilot pattern group having sub-carriers of a highest average power among all available pilot pattern groups.

12. The access method of claim 10, wherein the step of identifying the pilot pattern group is performed by

$n_{\mathrm{PG}}=\arg$

 

⁢

max m ⁢

∑

i = 1 N S ⁢

 

⁢

∑

p = 1 N P ⁢

 

⁢



Y ( p - 1 ) ⁢

M + m ⁡

( i ) 

2 , m ∈

{ 1 , 2 , …

⁢

 

⁢

N PG }

where n_PG is an index of an identified pilot pattern group, N_S is a number of symbols used to estimate the FH sequence set, N_P is a number of the pilot sub-carriers, Y_k(i) is a frequency-domain signal received on a k^th sub-carrier in an i^th symbol time, M is a minimum interval between the pilot sub-carriers, and N_PG is a number of the pilot pattern groups.

13. The access method of claim 10, wherein the step of identifying the pilot pattern group is performed by

$n_{\mathrm{PP}}=\arg$

 

⁢

max l ⁢

∑

i = 2 N S ⁢

 

⁢

∑

p = 1 N P ⁢

∑

k = 0 F - 1 ⁢

Y p ⁡

( i ) ⁢

Y p * ⁡

( i - k ) ⁢

d lp * ⁡

( i ) ⁢

d lp ⁡

( i - k ) , l ∈

{ 1 , 2 , …

⁢

 

, N pp }

where n_PP is an index of an identified pilot pattern group, F is a number of symbols unchanged in channel characteristics, N_S is a number of symbols used to estimate the FH sequence set, N_P is a number of the pilot sub-carriers, Y_k(i) is a frequency-domain signal received on a k^th pilot sub-carrier in an i^th symbol time, d_lk(i) is a pilot sample transmitted on the k^th pilot sub-carrier in an i^th symbol time, and N_PP is a number of the pilot patterns included in each of the pilot pattern groups.

14. The access method of claim 10, further comprising the step of correlating a preamble corresponding to the identified pilot pattern group with a predetermined number of multi-path signals for each of the plurality of symbols and determining a symbol having a largest correlation as a start point of a frame.

15. The access method of claim 10, further comprising the step of recovering data samples included in the symbols in an original order according to the FH sequence set.

16. The access method of claim 10, further comprising the steps of:

detecting a valid signal from a neighbor BS;

correlating the valid signal with all available pilot pattern groups;

detecting a pilot pattern group having a largest correlation; and

determining that the neighbor BS has the identified pilot pattern group and the identified pilot pattern.