WO2009038521A1 - Procédé et dispositif de réduction des interférences entre cellules - Google Patents

Procédé et dispositif de réduction des interférences entre cellules Download PDF

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Publication number
WO2009038521A1
WO2009038521A1 PCT/SE2008/050121 SE2008050121W WO2009038521A1 WO 2009038521 A1 WO2009038521 A1 WO 2009038521A1 SE 2008050121 W SE2008050121 W SE 2008050121W WO 2009038521 A1 WO2009038521 A1 WO 2009038521A1
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WO
WIPO (PCT)
Prior art keywords
transceiver
traffic
cell
services
scrambling
Prior art date
Application number
PCT/SE2008/050121
Other languages
English (en)
Inventor
Lei Xiao
Bin Xu
Jingyue Nie
Original Assignee
Telefonaktiebolaget Lm Ericsson (Publ)
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Telefonaktiebolaget Lm Ericsson (Publ) filed Critical Telefonaktiebolaget Lm Ericsson (Publ)
Priority to CN200880103974A priority Critical patent/CN101785207A/zh
Publication of WO2009038521A1 publication Critical patent/WO2009038521A1/fr

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J11/00—Orthogonal multiplex systems, e.g. using WALSH codes
    • H04J11/0023—Interference mitigation or co-ordination
    • H04J11/005—Interference mitigation or co-ordination of intercell interference
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/69—Spread spectrum techniques
    • H04B1/707—Spread spectrum techniques using direct sequence modulation
    • H04B1/7097—Interference-related aspects
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B2201/00—Indexing scheme relating to details of transmission systems not covered by a single group of H04B3/00 - H04B13/00
    • H04B2201/69—Orthogonal indexing scheme relating to spread spectrum techniques in general
    • H04B2201/707—Orthogonal indexing scheme relating to spread spectrum techniques in general relating to direct sequence modulation
    • H04B2201/70702—Intercell-related aspects

Definitions

  • a method and a device for reduced inter-cell interference are described.
  • the present invention discloses a method for use in a cellular telecommunications system which comprises a number of cells, in each of which there can be there a first and a second transceiver between which traffic can be exchanged.
  • the traffic between the transceivers can comprise at least a first and a second type of services.
  • TD-SCDMA Time Division Synchronous Code Division Multiple Access
  • scramble code and basic midamble code are sometimes used in neighbouring cells in order to decrease the inter-cell interference.
  • MBMS Multi-media Broadcast Multi-cast service
  • CCSA Choinese Communication Standardization Association
  • scramble code and basic midamble code are used for a group of adjoining cells which carry the same MBMS service in one and the same timeslot/frequency and which use one and the same spreading code.
  • users in a cell can receive MBMS signals from all surrounding cells, and use those received signals in order to perform so called soft combination.
  • Such a solution is offered by the present invention in that it discloses a method for use in a cellular telecommunications system.
  • the system in which the invention may be applied comprises a number of cells, in each of which there can be there a first and a second transceiver. Traffic can be exchanged between the two transceivers, so called scrambling codes are used for this traffic.
  • the traffic can comprise at least a first and a second type of services, and according to the inventive method, a first group of scrambling codes with a first scrambling code length is used for the first type of services, and a second group of scrambling codes with a second scrambling code length being used in a plurality of adjoining cells for the second type of services.
  • the length of the scrambling code can be "tailored" to a specific service, which, as will be shown in more detail in the detailed description below, can be used in order to reduce or eliminate inter-cell interference in, for example, MBMS applications within TD SCDMA systems.
  • the length of the first scrambling code is shorter than the length of the second scrambling code.
  • One option by means of which this can be achieved is to combine two or more codes from the first group.
  • a transceiver in a system in which the invention is used and which receives traffic of the second type from the second transceiver may also receive corresponding traffic from a transceiver of another cell.
  • the first transceiver can then either discard the corresponding traffic from the other cell, or combine the corresponding traffic from the transceiver in the other cell with the traffic from the second transceiver, depending on whether or not the traffic from the second cell will cause a positive contribution to the signal from the "own" cell, or cause interference.
  • the invention also discloses a transceiver for use in a system in which the invention is applied.
  • FIG. 1 shows a schematic view of a system in which the invention may be applied
  • Fig 2 shows a problem which the invention addresses
  • Fig 3 shows a first embodiment, of the invention
  • Fig 4 shows a rough flow chart of a method of the invention
  • Fig 5 shows a schematic block diagram of a transceiver of the invention.
  • Fig 1 shows a schematic view of a system 100 in which the invention may be applied.
  • the system 100 comprises a number of so called cells, one of which is shown as 130 in fig 1.
  • Each such cell 130 can comprise a number of users, also sometimes generically referred to as User Equipments, "UE".
  • UE User Equipment
  • One UE 120 is shown symbolically in fig 1.
  • the system 100 also comprises a controlling node for each cell, referred to as NodeB.
  • One such controlling node is shown as 110 in fig 1.
  • One of the functions of the controlling node 110 is to control traffic to and from users 120 in the cell 130. Traffic from the NodeB to the UEs is referred to as downlink traffic, DL, and traffic from the UEs to the NodeB is referred to as uplink traffic, UL.
  • TD SCDMA systems which do not offer MBMS services
  • different so called scramble codes and basic midamble codes are used in neighbouring cells in order to decrease inter-cell interference.
  • one specific scramble code and one basic midamble code are used in the same timeslot and frequency for all or a number of adjoining cells which offer MBMS services, as well as using the same so called spreading code, i.e. a code which is used for extending the available spectrum and for distinguishing different users from each other.
  • the use of the same codes in MBMS cells is due to a desire to allow UEs to receive signals (in the same timeslot and frequency) not just from the NodeB of "their" cell, but also from NodeBs of neighboring or adjoining cells, since this will enable the UEs to perform so called “soft combining" of the received signals from the different NodeBs, which will increase the signal level.
  • a problem which is caused by the principle of using the same codes is the following: if an MBMS signal from a NodeB is received by a UE at a point in time which is later than that from another cell, and the difference in time between the UE's reception of the two signals is greater than the length of the scramble code, the soft combining of the two signals will cause interference, instead of an increased signal level.
  • TD-SCDMA MBMS scrambling codes which have a length of 16 chips.
  • fig 2 shows a UE located in a cell ("Cell 2") in a TD-SCDMA MBMS system, with another, neighbouring cell which is referred to as Cell 1.
  • the DL signals from the NodeBs of the two cells are both received by the UE in Cell 2, as shown in the diagram of fig 2.
  • the data from the two NodeBs which should have been combined by soft combining in the UE is the data referred to as d1 , which is sent in so called CDMA "chips", each of which is coded with a different scrambling code.
  • the MBMS chip sequence for d1 is, as shown in fig 2, d1s1 , d1s2 d1s16.
  • the data for d1 from cell 1 arrives at the UE after the data sequence for d1 from cell 2 has been received at the UE, and at a point in time at which the UE has started to receive another data sequence, d2, from cell 2.
  • the delay shown in fig 2 between the arrival of the MBMS signal from cell 1 and cell 2 at the UE is thus 16 chips or greater, in other words at least the length of the scrambling code used in the system.
  • the NodeB of cell 1 i.e. the interfering and adjacent NodeB, will in most cases of course be more distant from the UE than the NodeB of the UE's "own" cell, which will cause the signal strength of the interfering signal at the UE to be lower than the signal from the UE's "own" NodeB, but the interference may still be a problem, in particular since a UE may be surrounded by multiple cells with interfering NodeBs.
  • the invention is intended to address the problem described above and shown in fig 2.
  • the invention will be described in more detail below, but a basic principle of the invention is that for TD-SCDMA MBMS traffic, a scramble code will be used which differs in length from that of the scramble code which is used for the other traffic in the cell , i.e. the "non-MBMS" traffic.
  • the length of the scrambling code which is used for non-MBMS traffic is shorter than the length of the scrambling code used for MBMS traffic, so that the effects of delays will not be as severe as those shown in fig 2.
  • a general aspect of the invention is to use scrambling codes of differing lengths for MBMS traffic and non-MBMS traffic.
  • the increased MBMS code length is achieved by means of combining two or more of the codes which are used for non-MBMS traffic.
  • the invention can also be illustrated with reference to fig 3, which shows the same situation as that of fig 2, but with a 32-chip length scramble code used for the MBMS traffic from the eNodeBs of cells 1 and 2.
  • fig 3 data sequences d1 and d2 are coded so that they become d1s1 , d1 ,s2 d1s16, and d2s17 d2s32, with dn denoting the nth data and sn denoting the nth chip of the scrambling code.
  • One way of obtaining the longer scramble code used for MBMS traffic in the example shown in fig 3 is to combine two of the scramble codes used for the non-MBMS-traffic. In such a case, two 16 chip long scramble codes will be combined, for example by letting d1 use scramble code 0 and letting d2 use scramble code 1 , d3 uses scramble code 0, d4 uses scramble code 1 , etc.
  • the simultaneously received MBMS data from cells 1 and 2 will cause a significantly lower degree of interference than previously, i.e. as shown in fig 1.
  • a UE which receives MBMS traffic from two cells may choose to either combine the MBMS traffic from the two cells, or to discard the MBMS traffic from one of the cells, suitably not discarding the MMBMS traffic from the "own" cell.
  • the choice may be made in a number of ways, for example the UE can "pre-process" received MBMS traffic by seeing if it has received such traffic from two sources, and then seeing if soft combining would cause a positive result or not.
  • a 32 chip long code is used for MBMS traffic.
  • a longer code is used for MBMS traffic than for non-MBMS traffic, a code of arbitrary length which exceeds 16 chips will be within the scope of the invention.
  • Fig 4 shows a rough flow chart of a method 400 of the invention. Steps which are options or alternatives are shown with dashed lines.
  • the inventive method 400 is intended for use in a cellular telecommunications system such as the one 100 in fig 1 , i.e. a system which comprises a number of cells 130, in each of which there can be there a first 110 and a second 120 transceiver between which traffic can be exchanged.
  • scrambling codes are used for the traffic, and the traffic can comprise at least a first and a second type of services.
  • a first group of scrambling codes with a first scrambling code length shown as S1-S16 in fig 2
  • a second group of scrambling codes with a second scrambling code length shown as S1-S32 in fig 3 being used in a plurality of adjoining cells for the second type of services.
  • the first scrambling code length is shorter than the second scrambling code length.
  • Step 420 shows that in one embodiment of the invention, the second scrambling code length is achieved by means of combining two or more codes from the first group.
  • Step 425 shows that in one embodiment of the invention, if the second transceiver 120 receives traffic of the second type from the first transceiver 100, it may also receive corresponding traffic from a transceiver of another cell, and according to the inventive method, the second transceiver can then either discard the corresponding traffic from the other cell or combine the corresponding traffic from the transceiver in the other cell with the traffic from the first transceiver.
  • the first scrambling code length of the first group of scrambling codes is 16 or shorter, and the second scrambling code length of the second group of scrambling codes is longer than 16.
  • the second transceiver is a controlling node 110 of a cell 130, which has one of its functions to control traffic to and from users 120 in the cell, and said first transceiver 120 is a user in the cell, so that the method is applied in the down link direction, DL, of the cell.
  • Step 435 shows that in one embodiment, the invention may be applied to a TD-SCDMA system, Time Division, Synchronous Code Division Multiple Access.
  • the first type of services can comprise voice and/or data traffic
  • the second type of services can comprise MBMS services, Multi-media Broadcast Multi-cast Service.
  • the second transceiver is a NodeB of a TD-SCDMA MBMS system
  • the first transceiver is a UE of such a system.
  • the invention also discloses both a first and a second transceiver for use in a system in which the invention is applied, i.e. a NodeB and a UE. Both of these transceivers will be shown and described with reference to fig 5, due to a basic structural similarity between them.
  • fig 5 shows a schematic block diagram of a transceiver 500 for use in a system in which the invention is applied.
  • the transceiver 500 will comprise an antenna, shown as block 510, and will also comprise a receive part 520 and a transmit part 530.
  • the transceiver 500 also comprises a control means 540 such as a micro processor, as well as a memory 550.
  • the transceiver 500 may also comprises an interface 560 towards other components in the system apart from the UEs, in the case that the transceiver 500 is a NodeB.
  • the transceiver 500 is intended for use as in a cellular telecommunications system such as the one 100 in fig 1 , i.e. a system comprises a number of cells 130, and in which system 100 scrambling codes are used for traffic.
  • the inventive transceiver 500 uses a first scrambling code with a length which is shorter than the length of the second scrambling code.
  • the transceiver 500 can use blocks 540 and 550 for obtaining the second scrambling code length by means of combining two or more codes from the first group.
  • the first scrambling code length of the first group of scrambling codes is 16 or shorter, and the second scrambling code length of the second group of scrambling codes is longer than 16.
  • the transceiver 500 is a controlling node such as the one 110 of a cell 130 as shown in fig 1 , which has one of its functions to control traffic to and from users 120 in the cell 130.
  • the transceiver 500 can also be a user terminal such as the one 120 of a cell 130.
  • the transceiver 500 is a UE, it will be able to use antenna 510 together with the receiver 520 for receiving traffic of the second type from a controlling node of its own cell as well as for receiving corresponding traffic from a controlling node of another cell, and will be able to use the controller 540 in order to either discard the corresponding traffic from said other cell or combining the corresponding traffic from the transceiver in the other cell with the traffic from the "own" controlling node.
  • the transceiver 500 is a transceiver in a TD- SCDMA system, Time Division, Synchronous Code Division Multiple Access, in which the first type of services comprises voice and/or data traffic, and the second type of services comprises MBMS services, Multi-media Broadcast Multi-cast Service.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Mobile Radio Communication Systems (AREA)

Abstract

Cette invention se rapporte à un procédé (400) destiné à être utilisé dans un système de télécommunication cellulaire (100), ledit système comprenant un certain nombre de cellules (130) qui peuvent chacune contenir un premier émetteur-récepteur (110) et un deuxième émetteur-récepteur (120) entre lesquels un trafic peut être échangé et, dans ledit système (100), des codes de brouillage sont utilisés pour ledit trafic. Le trafic peut comprendre au moins un premier et un deuxième type de services. Un premier groupe de codes de brouillage avec une première longueur de codes de brouillage (S1-S16) est utilisé pour ledit premier type de services, tandis qu'un deuxième groupe de codes de brouillage avec une deuxième longueur de codes de brouillage (S1-S32) est utilisé dans une pluralité de cellules contiguës pour ledit deuxième type de services.
PCT/SE2008/050121 2007-09-18 2008-01-31 Procédé et dispositif de réduction des interférences entre cellules WO2009038521A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN200880103974A CN101785207A (zh) 2007-09-18 2008-01-31 一种减少小区间干扰的方法及设备

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE0702081 2007-09-18
SE0702081-1 2007-09-18

Publications (1)

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WO2009038521A1 true WO2009038521A1 (fr) 2009-03-26

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WO (1) WO2009038521A1 (fr)

Citations (3)

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US6674790B1 (en) * 2002-01-24 2004-01-06 Meshnetworks, Inc. System and method employing concatenated spreading sequences to provide data modulated spread signals having increased data rates with extended multi-path delay spread
EP1796315A1 (fr) * 2004-09-28 2007-06-13 Matsushita Electric Industrial Co., Ltd. Systeme de transmission sans fil, station sans fil utilisee dans celui-ci et procede d utilisation
EP1582008B1 (fr) * 2003-01-10 2007-09-05 Interdigital Technology Corporation Estimation de donnees bi-etagee generalisee

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CN1192529C (zh) * 2002-01-23 2005-03-09 华为技术有限公司 一种在移动通信网络中提供实时广播业务的方法
CN1941687A (zh) * 2005-09-29 2007-04-04 华为技术有限公司 广播业务信道与非广播业务信道的复用方法
CN1972268A (zh) * 2005-11-25 2007-05-30 北京三星通信技术研究有限公司 在基于ofdm的系统中添加扰码的方法
CN100473182C (zh) * 2007-03-28 2009-03-25 中兴通讯股份有限公司 Td-scdma中采用单时隙网收发mbms的方法

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6674790B1 (en) * 2002-01-24 2004-01-06 Meshnetworks, Inc. System and method employing concatenated spreading sequences to provide data modulated spread signals having increased data rates with extended multi-path delay spread
EP1582008B1 (fr) * 2003-01-10 2007-09-05 Interdigital Technology Corporation Estimation de donnees bi-etagee generalisee
EP1796315A1 (fr) * 2004-09-28 2007-06-13 Matsushita Electric Industrial Co., Ltd. Systeme de transmission sans fil, station sans fil utilisee dans celui-ci et procede d utilisation

Non-Patent Citations (4)

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Title
"IPWIRELESS: ''Physical layer improvements for TDD MBMS''", 3GPP TS GRAN WG1#46, TDOC R1-062379 *
3GPP TS 25.223 V7.4.0 (2007-05); 3RD GENERATION PARTNERSHIP PROJECT; TECNICAL SPECIFICATION GROUP RADIO ACCESS NETWORK; SPREADING AND MODULATION (TDD) (RELEASE 7), May 2007 (2007-05-01), pages 14 - 15 *
3GPP TS 25.346 V7.4.0(2007-06); 3RD GENERATION PARTNERSHIP PROJECT; TECHNICAL SPECIFICATION GROUP RADIO ACCESS NETWORK; INTRODUCTION OF THE MULTIMEDIA BROADCAST MULTICAST SERVICE (MBMS) IN THE RADIO ACCESS NETWORK (RAN); STAGE 2 (RELEASE 7), June 2007 (2007-06-01), pages 28 *
ALOUINI, M.-S. ET AL.: "Communication Theory Mini-Conference", 6 June 1999, article "Performance analysis of generalized selective combining over Rayleigh fading channels", pages: 110 - 114 *

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