Qualcomm 1

Proposal for Unique Base Station (Sector) Identification

Source: Peter Gaal Suzanne Arcens QUALCOMM, Inc. QUALCOMM, Inc. pgaal@qualcomm.com sarcens@qualcomm.com (858) 845-7566 (408) 626-4431

July 14, 2003

San Francisco, CA 3GPP2, TSG-C, C16-20030714-003

NoticeQUALCOMM Incorporated grants a free, irrevocable license to 3GPP2 and its Organization Partners to incorporate text or other copyrightable material contained in the contribution and any modifications thereof in the creation of 3GPP2 publications; to copyright and sell in Organizational Partner’s name any Organizational Partner’s standards publication even though it may include portions of the contribution; and at the Organization Partner’s sole discretion to permit others to reproduce in whole or in part such contributions or the resulting Organizational Partner’s standards publication. QUALCOMM Incorporated is also willing to grant licenses under such contributor copyrights to third parties on reasonable, non-discriminatory terms and conditions for purpose of practicing an Organizational Partner’s standard which incorporates this contribution.This document has been prepared by QUALCOMM Incorporated to assist the development of specifications by 3GPP2. It is proposed to the Committee as a basis for discussion and is not to be construed as a binding proposal on QUALCOMM Incorporated. QUALCOMM Incorporated specifically reserves the right to amend or modify the material contained herein and nothing herein shall be construed as conferring or offering licenses or rights with respect to any intellectual property of QUALCOMM Incorporated other than provided in the copyright statement above.

July 14, 2003Qualcomm 2

Summary• Why do We Need Unique Base Station (Sector)

Identification?

• Effects of non-Unique Base Station Identification

• Typical cases of non-Unique Base Station Identification

• Recommendations

July 14, 2003Qualcomm 3

Why do we need unique base station (sector) identification?

• Position Location:– If Advanced Forward Link Trilateration (AFLT)

location technique is used, then the measured pilot phases, together with the known base station locations, are needed as inputs to the location solution. The base station location is read from a base station data base (base station almanac), which is indexed by the base station identification parameter values.

– If GPS location technique is used, then usually an initial approximate location estimate is used in determining the list of satellites visible to the user, their Doppler and/or approximate code phase. Usually, the approximate location is determined based on the location of the serving base station, which is read from the base station almanac.

July 14, 2003Qualcomm 4

Effects of non-Unique Base Station Identification inPosition Location

• If Advanced Forward Link Trilateration (AFLT) location technique is used, then the computed position will contain an unacceptably high error

• If GPS location technique is used, then the erroneous assistance data will prevent from completing the satellite measurements

Note that even if the incidence rate of non-unique base station identification cases is low in global terms, the effect will be still severe, since the positioning failure rate in the affected areas is nearly 100%.

July 14, 2003Qualcomm 5

Overhead Parameters Related to Base Station Identification

• The intent of the signaling standards was that every base station sector be uniquely identified by the SID/NID/BASE_ID triplet. The bit-width of the associated fields are:– SID: 15 bits– NID: 16 bits– BASE_ID: 16 bits

• There are other available parameters as well (e.g. PILOT_PN, BAND_CLASS, CDMA_FREQ) but unique base station identification is not ensured today even when all these parameters are used

July 14, 2003Qualcomm 6

Typical Cases of non-Unique Base Station Identification

• Within a SID, the same BASE_ID has multiple occurrences, while the NID field is not populated in the overhead message

• In a sectorized cell, all sectors are assigned the same SID/NID/BASE_ID

• Same SID is used by different carriers in different regions.

July 14, 2003Qualcomm 7

Proposed Parameter Assignment Rules

• (1) The same SID value must not be assigned to different carriers/license holders• (2) The same SID value must not be used in

different band classes• (3) The SID/NID/BASE_ID triplet must be

globally unique to identify individual sectors (in case of sectorized cells) and cells (in case of non-sectorized cells).• (4) Comply across all interfaces with the rule

specified in IOS: the 4 LSB's identify the sector within the Cell Identifier (BASE-ID).

July 14, 2003Qualcomm 8

Further Rules Recommended

• Unique base station identification is sufficient for position location purposes, as long as there exists an entry in the base station almanac corresponding to the serving sector; Imperfect data base management, however, may result in missing base station almanac entries. To get a coarse location estimate even in this case, either (or both) of the following two rules should be adopted:– (5) Populate the BASE_LAT and

BASE_LONG fields in the CDMA overhead message to give at least an approximate base station location– (6) Assign the NID values so that the SID/NID

pairs give a reasonably accurate geographical region identification