DE10110177B4 - A method of measuring and compensating for the propagation delay between nodes in a communication network - Google Patents

Abstract

A method for measuring and compensating propagation delay between nodes in a communication network, comprising:
Transmitting a loop delay measurement signal from a first node to a second node via a communication link;
Receiving the measurement signal at the second node and returning the signal to the first node together with an embedded value of a reverse delay time determined at the second node;
Receiving the measurement signal and the embedded inverse delay time at the first node;
Calculating the propagation delay by measuring the total delay time less the inverse delay time; and
Adding a delay component to a timing signal for the second node,
characterized in that the loop delay measurement signal is transmitted using Sa bits of a frame password protocol (FAS).

Description

Territory of invention

These The invention relates to communications networks that operate cellularly Include networks, but not limited to this are, and more precisely, a system and method for measuring and compensating variations in the propagation delay values between nodes in a communication network and especially between one Base station controllers and respective base stations, wherein the distances between the base station controller and the base stations they are the same.

background

Communication networks, like cellular systems, typically have a variety of cellular areas or cells, each cell providing services for an im essential circular geographical Area supplies. A base station is usually located in the middle of Cell and is designed to be a bidirectional communication with mobile or fixed remote Performing jobs within their coverage area. In a big one Geographical area is a multitude of cells partially overlapping arranged to provide the wide and continuous coverage of the area disposal to deliver.

typically, a base station controller becomes the overall controller of all base stations in a specific geographical area or city area make. One of the many functions of the base station controller is it, a timestamp or a synchronization signal to each Base station to give all units in the geographical area to have a common watch.

Of the Base station controller is often one of the base stations in but it can also be assigned to the geographical area a place away from all the base stations. Anyway the distance between the base station controller and each of the Base stations in the local geographic area covered by the Controller is controlled, probably not exactly the same.

As noted above, the reference clock time for each base station is one Derived master clock, which is typically assigned to the base station controller is. Since the distance from the base station controller to each base station is not the same, any reproductive delay will be in the communication link (T1, E1, etc.) between the base station controller and each base station mean that the timestamp for each base station is not will be synchronized.

at some solutions In the prior art, a special circuit has been added externally a multichannel transceiver installed on the base station controller, in an attempt to provide the synchronization. In such Systems were branded hardware and software procedures used to achieve the required functionality. As an alternative, schemes are based on satellite navigation systems (GPS), have been used in certain implementations, a similar one functionality to reach.

From WO 99/33207 A1 a synchronization for cellular telecommunication radio networks is known. This is performed between a master timing unit located at a control node of the radio network and a slave timing unit located either at the control node or at a controlled node such as a base station of the radio network. One of the two master or slave timing units serves as the initiating timing unit for transmitting a synchronization analysis command message which transmits a first parameter to the other timing unit serving as the responding timing unit. In response, the responding timing unit sends a synchronization analysis response message, and which returns at least one parameter, and preferably a third parameter, to the initiating timing unit. The initiating timing unit used parameters taken from the synchronization analysis response message to determine a synchronization setting value. The first parameter included in the synchronization analysis command message is a first timestamp value related to the time at which the synchronization analysis command message is transmitted from the initiating timing unit to the responding one. The second parameter, which is inserted in the synchronization analysis response message by the responding timing unit, is a second timestamp value relating to the time at which the synchronization analysis command message was received at the responding timing unit. The third timestamp value from the synchronization analysis response message relates to the time it was sent. The initiating unit determines a fourth timestamp value. The synchronization setting value is used to set the value of the system frame error of the corresponding timing unit. The master timing unit may be located at a base station controller, the slave timing unit may be located at a base station node be net. The synchronization message has an area for the payload, such as a previous head. The timestamp values occupy fields from the area of the payload.

Summary the invention

The The present invention is intended to disclose certain aspects of Synchronization between base stations to solve, in situations where multiple base stations with a single base station controller connected, e.g. E1 connections are used, and in particular, when the electrical connections between the base station controller and individual base stations have different lengths.

The The present invention provides a formal approach to the above solve the problem mentioned. An embedded protocol within the multichannel transceiver defines the required handshaking between the base station controller and the individual base stations, where FAS / NFAS word bits of a frame password protocol (FAS: Frame Alignment Signal = NFAS: Non-Frame Alignment Signal = frame message word) and in particular the Sa bits are used, the one not disturbing Procedure for the Measurement of the propagation delay. The further integration of the measuring circuit in a multichannel transceiver leads to an implementation for the connectivity between base station controller and base station is highly suitable.

Therefore will according to one first aspect of the present invention, a method of measuring and Compensate the propagation delay between nodes in a Communication network available that has: transmit a loop delay measurement signal from a first node to a second node via a communication link using Sa bits of a frame password protocol (Frame Alignment Signal: FAS); Receive the measurement signal the second node and returning the signal to the first node together with an embedded one Value of a reverse delay time, the has been determined at the second node; Receiving the measuring signal and the embedded inverse delay time at the first node; To calculate the reproductive delay circulating between the nodes by measuring the total delay time less the inverse delay time; and adding a delay component to a timing signal for the second node.

According to one second aspect, the first node is a base station controller in a wireless communication network and the second node one Base station.

According to one Third aspect of the present invention is a method for Calculating and compensating respective relative propagation delays between a base station controller and a plurality of base stations provided in a communication system in which each the base stations over separate communication links with the base station controller is in communication.

According to one another aspect is for each communication link has a separate propagation delay value calculated.

According to one Another aspect of the present invention is a method for Measuring and compensating for different propagation delay times between a base station controller and a plurality of base stations provided in a communication network, comprising: transmitting a common HDLC timing message as a measuring signal.

According to one Another aspect of the invention will be a system for measuring and compensating the reproductive delay provided between nodes in a communication network, comprising: a transmitter at a first node for transmitting a loop delay measurement signal from the first node to a second node via a communication link using Sa-bits of a frame password protocol (frame Alignment signal: FAS); a receiver at the second node for receiving the measurement signal and to send back the same at the first node together with an embedded one Value of an inverse delay time, which has been determined at the second node; a receiving device at the first node for receiving the measurement signal and the embedded one Reverse delay time; computing means at the first node for calculating the propagation delay Measuring the total delay time less the inverse delay time; and means at the first node for adding a delay component.

Summary the drawings

The The invention will now be described in further detail with reference to the attached drawings described, wherein:

1 a higher reference model of the base station controller / base station system according to the present invention;

2 Figure 3 is a flowchart illustrating the propagation delay measurement and timing adjustment measurements;

3 is a time chart showing the device delays and the circulation propagation delays;

4 FIG. 4 is a block diagram of a hadye implantation according to an embodiment of the invention; FIG.

5 illustrates in block diagram format the delay compensation within the base station controller; and

6 illustrates in block diagram format the delay compensation in the base station.

Precise description the invention

The concept presented for loop delay compensation in accordance with the present invention is roughly illustrated in the reference model disclosed in US Pat 1 is shown. The Base Station Controller (BSC) 12 can have a multichannel E1 (or T1) transceiver and is compatible with the base stations 14 connected by E1 (T1) connections L1 to L3. The base stations (BS) 14 As will be apparent to those skilled in the art, a single or multi-channel transceiver could have, for the sake of simplicity, a single channel in 1 illustrates (E1 is used in the model). The multichannel transceiver in the BSC is normally the master, and each of the base stations derives their synchronization timing from the master. The derived timing is used, for example, to drive a radio circuit in the base stations. Certain radio schemes require that the radio frames transmitted by the different base stations be synchronized. Examples of such schemes include wireless technologies, as well as DECT, PHS, PCS, etc.

As discussed above, it is likely that the distances between the individual base stations and the base station controller differently are, and this is natural depending on the network design. This present invention provides an implementation method to disposal, where a compensation process is carried out at the BSC to ensure that an alignment the timing frame at all base stations despite a difference in the loop lengths is present.

The protocol between the BSC and the BS for purposes of delay measurement and adaptation will be described in detail below in connection with the flowchart of FIG 2 explained.

The Initiate the loop delay measurement at the end of the Masters (BSC) could be initiated by the system controller or could be Part of the initialization procedure in the device, depending on the control input for the Mode selection. The procedure is initiated after the master end a basic frame alignment on the selected links from the Base stations reached.

The FAS / NFAS Sa bits are used to transmit (or send) an HDLC based message to the selected base stations. Since the BSC and the BS are typically supplied by the same vendor in most of the cases, it is believed that using the Sa-bits will not be a problem for this situation. In this implementation, the use of Sa-bits does not create additional bandwidth for the measurement purpose and will allow payload time slots to move normally both in BSC to BS and BS to BSC under mode 1 or normal operation, as explained below. However, the operation requires in mode 2 a remote loop back to the BS, and this will disrupt communication from the BS to the BSC.

At the base stations, receiving an HDLC message on the Sa bits will cause the transceiver to either enter mode 1 or mode 2 will occur, with the frames being transmitted to the BSC having a fixed offset with respect to the incoming frames. This fixed offset will be the same at all of the base stations, so the compensation process will be applied to account for only propagation delay distortion and not delays resulting from device related factors (ie dampers for flutter, slip buffers, etc.). The transceivers at the BSs indicate to the BSC that they are either in the mode 1 or in the mode 2 (ie backward loop) by sending an acknowledge (ACK) message over the Sa bits to the BSC.

The BSC continues to make delay measurements based on the orbital value and locks the results, taking into account the selected connections. These delay values can be processed in hardware using an embedded algorithm for normalization, and the delay blocks are automatically programmed into the transmission paths to the BSC-to-BS connections. Another option is to interrupt the system controller and process the delay values with system software.

Afterwards the successful normalization will be a message from the BSC to the BS some sent. The base stations can start by using the use derived timing from the connections to the radio frequency transceivers To drive communication with mobile agencies. Verification or more iterations can be made by repeating the measurement of propagation delay becomes.

When a variant of the above scheme, the BSC may use the base stations instruct to assign the high frequency frame by appropriate bit times accelerate or delay, wherein the aforementioned Sa bits are used.

The three main aspects of the implementation details for the present Invention can summarized become: measurement of reproductive delay in circulation; an algorithm to individual connection delays to calculate; and compensation of the delay on individual connections.

For the measurement of the propagation delay in circulation (E1 case) it is assumed that the typical loop length between the BSC and the BS is on the order of a few kilometers (about 10). If a delay factor of 5 μs / km is assumed, a maximum delay of 100 μs in a 10 km loop will be experienced. 3 shows a typical timing chart. The Fref in the top line is the reference frame pulse in a multi-channel device input on the system side. The period of 125 μs is based on a reference signal of 8 kHz. The timing chart of the 3 Assume that the recovered frame sync signals (rsync1 to rsync3) arrive in the direction of the BS to the BSC before the next frame pulse occurs on Fref, ie, it is assumed that the propagation delays in the round trip plus the device delays (D) on all the Connections less than 125 μs (This assumption would be true in most cases, but in the following paragraph an alternative method is explained for the cases where the "rsync" signal arrives at Fref after the next pulse.) It may be in 3 It can be seen that compound # 3 has a maximum propagation delay. Therefore, if delay factors having the values C1 and C2 are respectively inserted into the connection # 1 and the connection # 2, then the received frames at the base stations (FIG. 1 to 3 ) all be aligned with each other.

One alternative method is a 4 kHz frame reference signal (FAS or NFAS in E1), So that the recovered frame synchronization signals (rsync1 to rsync3) a Duration of 250 μs will have. This procedure will provide an accurate estimate of the Measurement of the propagation delay in circulation for delays greater than Deliver 125 μs. It should be noted that a Payload loop back (BSC -> BS> BSC) required will be for this process to be successful.

4 Figure 4 shows a physical embodiment of an implementation for measuring the propagation delay built into the multi-channel E1 transceiver and applicable to both values of Fref (ie 8 kHz or 4 kHz). Each of the framers in the multi-channel apparatus has a corresponding counter, counter 1 through counter n. In this implementation, a 4096 MHz clock is used for counting. The signals Fref and Rsync are used to start and stop the counter. In addition, there is a global release. The arrival of the rsync pulses will stop the counters and the values P1 to Pn representing the number of clock pulses of 4,096 MHz occurring in the interval between Fref and Rsync will be latched and used in further calculations.

Of the Algorithm for calculating the individual connection delays can be implemented either by built-in hardware or software become. The goal here is the extra delays calculated in the [n-1] compounds of the BSC to BS pathways, to align the E1 frame pulses received at the BS.

at In the above algorithm, Pm is the maximum count that represents the connection for the most 4 MHz clock pulses during of the interval counted were. The delay value C for the Link n is less Pm of the count for the special link (Pn) divided by 2. The values C1 and Cn are the results of each the calculations for the connection # 1 to connection #n.

The compensation of the delay on individual connections can be implemented by different methods as described in US Pat 5 and 6 are shown. In 5 the delays are implemented in the BSC (ie the delays are implemented within the multi-channel device). In 6 the delays in the base stations are implemented.

In 5 For example, a frame encoder for each connection contains a programmable delay element which loads the values C1 to Cn into the delay elements through hardware or software.

In the implementation that in 6 is illustrated, the value Cn for each base station is transmitted via the Sa bits in the HDLC from the BSC to the designated BS. The E1 (T1) receiver in the base station has a built-in programmable delay unit. The extracted frame pulse from the BSC is delayed by the value Cn, and the delayed frame pulse is then used to drive the radio.

Even though certain embodiments of the invention have been described and illustrated It is clear to the experts that many changes can be made to the concept without you removed from the idea of the invention. For example, the application of the Concept of the present invention extended to implementations which use multi-channel T1 / JT1 transceivers, multi-channel E3 / DS3 and SDH. It should be understood, however, that such changes fall within the full scope of the invention as they pass through the attached Claims defined is.

Claims (7)

A method of measuring and compensating the propagation delay between nodes in a communication network, comprising: transmitting a loop delay measurement signal from a first node to a second node over a communication link; Receiving the measurement signal at the second node and returning the signal to the first node together with an embedded value of a reverse delay time determined at the second node; Receiving the measurement signal and the embedded inverse delay time at the first node; Calculating the propagation delay by measuring the total delay time less the inverse delay time; and adding a delay component to a timing signal for the second node, characterized in that the loop delay measurement signal is transmitted using Sa bits of a frame password protocol (FAS). The method of claim 1, wherein the first node a base station controller in a wireless communication network is and the second node is a base station. The method of claim 2, wherein there are a plurality of base stations, each in communication with the base station controller via separate communication links. Method according to claim 3, wherein for each communication connection a separate propagation delay value is calculated. Method according to Claim 4, in which the measuring signal a message according to the HDLC standard (high level data link control). The method of claim 3, wherein the base station controller sends a frame reference signal with a constant frequency and Receive frame synchronization signals from respective base stations, wherein the time between the frame reference signal and the respective frame synchronization signals the delay for every Represents base station. System for measuring and compensating the propagation delay between Nodes in a communication network, with: to a transmitter a first node for transmission a loop delay measurement signal from the first node to a second node via a communication link; one receiver at the second node for receiving the measurement signal at the second node and to send back of the signal to the first node together with an embedded one Value of an inverse delay time, which has been determined at the second node; a receiving device at the first node for receiving the measurement signal and the embedded one Reverse delay time; and a computing device at the first node for calculation the reproductive delay by measuring the total delay time less the inverse delay time; and a device at the first node for adding a Delay component marked by using Sa-bits of a frame password protocol (FAS) for the transfer the loop delay measurement signal.