KR20020052561A - Method for Measuring Position in Time Division Duplex mode - Google Patents

Abstract

PURPOSE: A method for measuring positions at a TDD(Time Division Duplex) mode is provided to use an OTDOA(Observed Time Difference Of Arrival) at a narrowband TDD mode having a different structure from a wideband TDD mode. CONSTITUTION: In a TDD mode having a low-speed chip rate, a radio frame, a length of 10ms, is composed of two sub frames having a length of 5ms. Each sub frame is divided into 7 traffic slots and 3 time slots. Slot numbers(TsN) are allocated to the 7 slots respectively. The 3 time slots having special functions are located between slot numbers Ts0 and Ts1. A guard period and a DwPTS(Downlink Pilot Time Slot) are regularly located after Ts0 so that a Node-B can execute a synchronization procedure and a user who transmits an UpPTS(Uplink Pilot Time Slot) cannot interrupt a user from transmitting another user's DwPTS.

Description

Method for measuring position in time division duplex mode

The present invention relates to a next generation mobile communication system, and more particularly, to a position measurement method in a time division duplex (TDD) mode having a low chip rate of 1.28 Mcps.

In general, the conventional position measurement method includes a cell identifier-based position measurement method and an Observed Time Difference of Arrival (hereinafter, referred to as IPDL). , OTDOA), a method using a network assisted GPS, an Arrival Of Angle (hereinafter referred to as AOA), and the like.

In particular, a position measurement method using an Observed Time Difference of Arrival-Idle Period Downlink (hereinafter, abbreviated as OTDOA-IPDL) in the downlink idle period is a downlink common pilot channel received at the UE. This principle is illustrated in FIG. 1 in a manner of using OTDOA of a (Common Pilot Channel; hereinafter abbreviated as CPICH) signal.

1 is a diagram illustrating a UE location measurement principle using OTDOA.

As shown in FIG. 1, first, an OTDOA value measured in a position measurement method using OTDOA is combined with an actual relative transmission time difference of a downlink channel signal and a geographical position of an observed transmitter, and thus, a user equipment (hereinafter referred to as UE). (Abbreviated as D)). The OTDOA measurements of a pair of downlink channel signal transmissions plot a hyperbolic constant difference in which the UE can be located. The location of the UE is then determined by the intersection of these hyperbolas for at least two pairs of Node-Bs.

For the OTDOA approach, the accuracy of the position measurement depends on the accuracy of the time measurement, the relative position of the Node-B considered, and multipath propagation.

The next basic OTDOA measurement is sent to the Position Calculation Function (hereinafter referred to as PCF) block in the Serving Radio Network Controller (hereinafter referred to as SRNC) that is responsible for servicing the area. .

The PCF block consists of OTDOA measurements, commonly known transmitter positions from information from the Global Positioning System (hereinafter referred to as GPS) receiver, and the relative time difference between the transmitted signal (abbreviated as RTD). Combine to determine the location of the UE.

In order to use the UE positioning method using the OTDOA, RTDs of downlink transmission signals should be provided to the PCF block, if the system side (Universal Terrestrial Radio Access Network; hereinafter, UTRAN) transmitter is asynchronous. RTDs of downlink transmission signals change with time. Therefore, a regular RTD measurement should be made, and accordingly, the PCF block needs to update the measured RTD values.

However, in some wireless environments, a UE, which is a location measurement target, may not measure downlink CPICH from another specific Node-B. This is the case when the UE enters a certain Node-B and is close to the Node-B, since the receiver of the UE is blocked by the strong local transmission signals of the Node-B. This is called the signal's reachability problem.

The OTDOA-IPDL method uses an idle period (IP) in order to increase the reachability of such a signal in the OTDOA method.

Each Node-B in the IPDL stops transmitting signals for that short period. In this manner, UEs in a cell region may measure transmission signals of other Node-Bs during an idle period (IP) of a specific Node-B, thereby improving signal reachability. As a result, the signal's reachability problem can be overcome.

And also RTD measurements are made during the idle period (IP). Since the OTDOA-IPDL scheme is based on downlink transmission, it is possible to more effectively provide location information service for many UEs simultaneously.

On the other hand, there is currently no method proposed as a location information service in narrowband TDD (1.28Mcps). Therefore, OTDOA, which is a problem of the prior art, is used for frequency division duplex (hereinafter referred to as FDD) location information service and is also used as a basic principle in time division duplex (hereinafter abbreviated as TDD). In this paper, we describe IPDL, which is a problem of the conventional method in overcoming the reachability that occurs in the application of OTDOA, rather than the difference in location information service method due to the difference in structure between FDD and narrowband TDD. .

The location measurement method by OTDOA-IPDL should measure downlink signals to the UE and combine them to calculate the location of the UE. That is, the complexity of the UE is greatly increased. And, in case the UE does not receive CPICHs transmitted from other Node-Bs as the UE enters deep into the arbitrary Node-Bs (which cannot perform ODOA), Node-Bs are instantaneously constant in an arbitrary order. The slot mode (Slotted Mode or Compressed Mode), which transmits no signal in symbol units, is used as an optional method of OTDOA, and there are many problems in application considering that the operation effectiveness of this slot mode is questionable. I think.

In addition, unlike the wideband TDD (3.84Mcps), the narrowband TDD does not have a CPICH and a synchronization channel (hereinafter, abbreviated as SCH), and the DwPTS performs the same function. Therefore, in order to apply OTDOA, which is the basic location information service method of the FDD method, a different method from the FDD should be used.

SUMMARY OF THE INVENTION An object of the present invention has been made in view of the above points, and is a position measurement in time division duplex mode, which is suitable to use the observation time arrival difference (OTDOA) in a narrowband TDD scheme having a structure different from that of the wideband TDD scheme. To provide a method.

Another object of the present invention is to provide a position measurement method in time division duplex mode suitable for overcoming the reachability of observation time arrival difference (OTDOA) in a narrow band TDD scheme having a structure different from that of the wide band TDD scheme.

A feature of the UE's location measurement for achieving the above object is that the user measures the reception time of the downlink pilot time slots from a plurality of base stations (Node-B), and the measured reception times to the system (UTRAN) ) And determining, by the system, the intersection of the graph generated by the reception times as a user location.

Preferably, the graph is generated by connecting points at which reception times of the pilot time slots are the same, and all other users of the base stations where the user is located may select uplink pilot time slots for a predetermined time while the system measures the position of the user. While not transmitting.

1 illustrates the principle of user device position measurement using OTDOA.

2 illustrates a radio frame structure in a typical 1.28 Mcps time division duplex (TDD) mode.

3 is a diagram illustrating the structure of a subframe shown in FIG. 2;

4 is a diagram illustrating the structure of a time slot shown in FIG. 2;

FIG. 5 is a diagram showing the structure of an UpPTS time slot shown in FIG. 2; FIG.

FIG. 6 is a diagram showing the structure of a DwPTS time slot shown in FIG. 2; FIG.

Hereinafter, a preferred embodiment of a method for measuring a location of a UE according to the present invention will be described with reference to the accompanying drawings.

2 is a diagram illustrating a radio frame structure in a general 1.28 Mcps time division duplex (TDD) mode.

3 is a diagram illustrating a structure of a subframe illustrated in FIG. 2.

Referring to FIG. 2 or 3, a radio frame in a TDD mode having a low chip rate is 10ms long, and the radio frame is composed of two subframes 5ms (6400 chips) long. The subframe is divided into seven traffic slots and three time slots with special functions. In the TDD mode having a low chip rate, the frame structure is appropriately divided into uplink or downlink time slots so that a symmetrical or asymmetrical structure is provided. Can be operated. In this case, each of the seven slots is assigned a slot number (TsN; N is an integer increasing from 0 to 6), where Ts0 time slot is assigned to downlink and Ts1 time slot is assigned to uplink. In addition, three time slots having special functions are located between the time slots of Ts0 and Ts1. A guard period (hereinafter, abbreviated as GP) and a downlink pilot time slot (DwPTS) are provided. Is fixed after the Ts0 time slot in the subframe so that the user does not lose synchronization, and the base station Node-B performs the synchronization procedure (via the DwPTS channel). It also prevents users transmitting Uplink Pilot Time Slots (hereinafter, referred to as UpPTS) from interfering with users who transmit DwPTS of other users.

That is, there are 75 GPa between the DwPTS and UpPTS. This is provided for secure transmission to all UEs in a cell since DwPTS is very important for cell discovery or channel estimation. This 75 ms time guarantees a cell radius of 11.25 km according to the following equation.

, c is the velocity of light

Here, d _max represents the maximum cell radius, and t_gap represents the time difference between the potentially downlink signal and the potentially uplink signal.

That is, all the surrounding UEs do not transmit a signal for 75ms after the DwPTS is transmitted from the Node-B. After that UpPTS, Ts1 is transmitted from the UEs. The signal is theoretically transmitted DwPTS without interference from the UE up to a cell radius of 11.25 km.

4 is a diagram illustrating a structure of a timeslot shown in FIG. 2.

Referring to FIG. 4, a timeslot generally includes two data symbol fields having 352 chips, a midamble field transmitted between these fields, and a 16-chip GP field.

Here, the midamble (144 chips) is the same field as the pilot symbols of the FDD, and the base station measures the midamble field of each user located in the same slot to estimate the power level and shifted transmission timing. To be able. In addition, by transmitting synchronization shifting and power control signals on the next downlink time slot, uplink synchronization is maintained by allowing the user to appropriately adjust the transmission (Tx) timing and transmission power level.

For reference, the UpPTS includes a SYNC1 field (128 chips) and a GP field (32 chips) as shown in FIG. The UpPTS is a time slot having a total length of 125us, and a user may send the UpPTS once every 5ms subframe. The UpPTS consists of a SYNC1 field (128 chips) and a GP field (32 chips). The UpPTS is a time slot having a total length of 125us, and a user may send the UpPTS once every 5ms subframe. Here, SYNC1 is composed of an orthogonal gold sequence of 128 chips, and eight orthogonal gold codes are allocated per base station (or cell).

After measuring transmission timing and power level of the UpPTS, the base station Node-B issues transmission timing adjustment and power adjustment command through a downlink fast physical access channel (FPACH). This information allows the user to signal at the correct transmission timing and power over the physical random access channel (PRACH) in uplink.

In addition, the DwPTS is a timeslot having a total length of 75us as shown in FIG. 6, and a user may send the DwPTS once every 5ms subframe. The DwPTS consists of a SYNC field (64 chips) and a GP field (32 chips). This DwPTS is required for initial cell search and channel estimation in the narrowband TDD scheme.

The UE location measurement method in narrowband TDD having such a radio frame structure is performed by the following procedure.

Default geolocation service behavior

TDD system is basically synchronized between Node-B. In addition, the UE receives the DwPTS from the current serving Node-B and performs cell discovery through the UE. The UE will also receive DwPTS from other Node-Bs in the vicinity. At this time, a hyperbolic curve can be obtained as shown in FIG. 1 by using differences in arrival times of DwPTSs from a Node-B of a UE, which is a point where a difference in arrival time from a neighboring Node-B is constant. The UE sends these observations to the system side (Universal Tessestrial Radio Access Network (UTRAN)), which determines the intersection of these two or more hyperbolas as the location of the UE currently looking for.

That is, the initial cell search of the narrowband TDD system is performed by using the SYNC of the DwPTS, and an arbitrary Node-B selects one of 32 PN (Pseudo Noise) sequence sets and transmits it to the UE through the DwPTS. Therefore, the UE finds a PN sequence whose value is maximum by using one or more matched filters matching the SYNC code. That is, the UE finds out of a total of 32 SYNC codes using the matched filter. Thereafter, the UE receives the midamble of the primary common control physical channel (hereinafter, P-CCPCH). The P-CCPCH is allocated to Ts0, which is a slot before DwPTS. In the current narrowband TDD, four basic midambles are allocated per SYNC, and there are a total of 32 SYNC codes, so there are a total of 128 midambles. Divide the base midamble code number by 4, which is the SYNC code number. SYNC codes and basic midamble code groups are mapped one-to-one. That is, when the SYNC is detected, four basic midambles are determined among the 128 basic midambles. The UE then finds one of the four basic midamble codes through trial and error, and the same basic midamble is used over the frame. Since each basic midamble code is associated with a scrambling code, the scrambling code can be known at that moment. Afterwards, to find out more detailed broadcast information, broadcast channel information (hereinafter, abbreviated as BCH) of the P-CCPCH is read. Through this process, the UE synchronizes to the cell where it is currently and performs cell recognition.

How to overcome reachability

If the UE to find goes deep into any Node-B, it becomes difficult for the UE to receive signals from other Node-Bs. In this case, the OTDOA method becomes impossible, which is called reachability problem.

In other words, all the surrounding UEs do not transmit a signal for 75ms after the DwPTS is transmitted from the Node-B. After that UpPTS, Ts1 is transmitted from the UEs. The signal is theoretically transmitted DwPTS without interference from the UE up to a cell radius of 11.25 km. However, when a UE goes deep into a cell, the UE receives DwPTS from another Node-B and is interfered with by surrounding UpPTSs. Therefore, there is a high probability of not receiving enough DwPTS signals necessary for OTDOA. As a method for overcoming such reachability, in the present invention, in the UE location service mode, the UTRAN does not transmit UpPTS for several sub-frames, that is, during location service, in the Node-B where the UE to be searched for is located. Do not.

The UpPTS is not required for every subframe since it is required for uplink synchronization and random access and handover. If the UpPTS is not transmitted as shown in Table 1 below, the DwPTS may be transmitted without interference by twice the distance in theory than the signal can be transmitted without interference. Therefore, it is possible to increase the probability that the UE receives the DwPTS of the neighbor cell. This approach overcomes the reachability problem.

Occation Cell radius If interference between UpPTS and DwPTS is not allowed 11.25Km Interference between UpPTS and DwPTS is allowed and no interference is allowed for TSO 22.5Km If interference between Ts1 and DwPTS is allowed, but not for others 30km

The method for measuring a location of a UE according to the present invention described above can perform a location measurement service in a narrow band TDD using the OTDOA method, and in the reachability problem caused by using the OTDOA method, Unlike the conventional IPDL scheme, there is no signal disconnection, and it is possible to simply overcome the reachability problem without further structural change or complexity of the narrowband TDD system.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the spirit of the present invention.

Therefore, the technical scope of the present invention should not be limited to the contents described in the embodiments, but should be defined by the claims.

Claims (3)

Measuring a reception time of downlink pilot time slots from a plurality of base stations (Node-Bs) by the user; Transmitting the measured reception times to a system (UTRAN); And determining, by the system, an intersection point on the graph generated by the reception times as a user position. The method of claim 1, wherein the graph is generated by connecting points at which reception times of the pilot time slots are the same. 2. The method of claim 1, wherein all other users of base stations with the user do not transmit uplink pilot time slots for a predetermined time while the system measures the user's location. .