HK1020125A - E1 compression control method - Google Patents

Description

E1 compression control method

Technical Field

The present invention generally relates to the field of telecommunications systems. In particular, the present invention relates to an N: 1E 1 compression process.

Technical Field

In the early days of telecommunications, a single information channel was carried on a single copper wire medium. Since the largest part of the cost is the material and construction of the physical link, telephone engineers have devised ways to combine multiple channels onto one physical link. Frequency Division Multiplexing (FDM) and Time Division Multiplexing (TDM) techniques have been invented that can multiplex multiple analog and Pulse Code Modulated (PCM) digital signal streams, respectively, into one. For digital signals, the TDM hierarchy is DS0 through DS4, where DS0 is a single channel of 0.064 mbits/sec, and DS4 is 4032 message channels (DS0) multiplexed together.

In the international telephone system, a similar TDM scheme is used according to the 32-channel format. The international digital system proposed by the G.700 series of International telecommunication Union CCITT is commonly referred to as E1 or CEPT-1. The E1 signal is based on a 32-channel or 32-slot packet (block), where slot 0 and slot 16 are typically used for control and signaling, respectively.

While the U.S. and international digital systems provide multiplexing of DS0 or E1 signals, resulting in higher rate signals, it is desirable for the telecommunications physical link to be more efficient. The ability to facilitate the transmission of high density voice and data channels may reduce the number of physical links, thereby further reducing the long haul required to connect calls.

Disclosure of Invention

Therefore, a compression method that can concentrate multiple E1 signals onto one E1 link is needed.

In accordance with the present invention, an N: 1E 1 compression method is provided that eliminates or substantially reduces the disadvantages associated with prior methods.

In one aspect of the invention, an N: 1E 1 compression method includes the steps of: receiving N incoming E1 signals; extracting a plurality of voice/data channels from the N incoming E1 signals; the control, monitoring and status information channels are also extracted from the N incoming E1 signals. Then, compressing the data in the extracted voice/data channel; generating and incorporating control, monitoring and status information into a predetermined channel of a compressed E1 signal; and incorporating the compressed data into the available channels of the compressed E1 signal.

In another aspect of the invention, four E1 signals are ADPCM compressed and combined into one available channel for compressing the E1 signal. Digital language interpolation may also be used.

In yet another aspect of the present invention, the compressed E1 signal includes control, monitoring and channel status information embedded in four E1 signals in predetermined channels of the compressed E1 signal.

Brief description of the drawings

For a better understanding of the present invention, reference is made to the accompanying drawings, in which:

FIG. 1 is a simple block diagram illustrating a general application of a transcoder constructed in accordance with the principles of the present invention;

FIG. 2 is a block diagram illustrating the inputs and outputs of a transcoder constructed in accordance with the principles of the present invention;

FIG. 3 is a block diagram of an embodiment of a transport encoder;

FIG. 4 is a block diagram illustrating a compressed data path;

FIG. 5 is a block diagram illustrating a compressed data path;

FIG. 6 is a diagram illustrating a bitmap of four uncompressed E1 to one compressed E1;

FIG. 7 is a diagram illustrating a bitmap of control and additional information for four uncompressed E1 into slots in compressed E1; and

FIG. 8 is a diagram illustrating bit mapping of Channel Associated Signaling (CAS) information of four uncompressed E1 to slots in compressed E1.

Detailed description of the invention

Fig. 1-8 illustrate a preferred embodiment of the present invention, and like reference numerals are used to refer to like and corresponding parts of the various drawings.

Referring to fig. 1, there is shown a generic telephony application 10 of the transcoder 12 of the present invention. Transcoder 12 is coupled to Channel Banks (CB) 14 and 16 which digitize and multiplex multiple voice and data signals onto a single E1. The voice and data signals may come from a telephone set 18, a facsimile machine (FAX)20, and a Data Terminal Equipment (DTE) 22. Transcoder 12 may also be coupled to a digital private branch exchange (PBX)24, and digital private branch exchange 24 may be coupled to telecommunications equipment including telephone 18 and modem 26. The channel bank 14 and digital private branch exchange 24 are coupled to the transcoder 12 by E1 links 30-36, each of which transports data and voice channels in E1 format.

The transcoder 12 compresses the four E1 signals on the links 30-36 into one E1. Transcoder 12 is coupled to remote transcoder 40 by an E1 link 42 for transmission of compressed E1(CE 1). The E1 link 42 may be any transmission medium, including copper, optical, and wireless. In the event of a failure of link 42, a redundant link 43 is also provided. The teletransport encoder 40 decompresses the compressed E1 into four E1 signals and places them on the E1 links 44-48 connecting the channel banks 50 and 52 and the digital private branch exchange 54, the channel banks 50 and 52 and the digital private branch exchange 54 being coupled to telecommunications equipment including telephones 60, fax machines 62, modems 64 and data terminal equipment 66.

In a similar manner, voice and data may be compressed onto the E1 link 42 with the remote transport encoder 40 and then decompressed into respective E1 signals with the transport encoder 42.

A plurality of transcoder 70 may be coupled to transcoder 12 in a daisy-chain fashion, such as via an RS-232 link, for transmitting control and/or alarm information, for example. Management/control terminal 72 is coupled to transcoder 12. At the management/control terminal 72, programming parameters are entered and the transcoder 12 and 40 are controlled. The remote transport encoder 40 is monitored by communicating monitoring information with the remote transport encoder 40 using the bandwidth of the compressed E1. Transcoder 12 and 40 may also be monitored via a remote terminal 74 coupled to transcoder 12. In this manner, an operator may access transcoder 12 and/or transcoder 40 by dialing a number through remote terminal 74.

Fig. 2 shows the important input and output signals of the transcoder 12. The transport encoder 12 receives or provides N pieces of bi-directional uncompressed E1 information (shown as UE1_ A, UE1_ B, UE1_ C and UE1_ D). Transport encoder 12 also receives or provides two bi-directional compressed E1 signals CE _ ACTIVE and CE _ STANDBY. The compressed E1 signals CE _ ACTIVE and CE _ STANDBY are redundant signals that are provided as spares for each other. A dc or ac power source and its backup power source 85 provide power and backup power to the transcoder 12.

SYNC _ IN is an external reference clock signal that can be used to generate a system synchronization clock signal. The generated system synchronization clock signal may be provided as a SYNC _ OUT clock signal to other co-located transcoder 70 (fig. 1) daisy-chained with transcoder 12 to achieve synchronization with a single timing source.

OFFICE _ ALM is an output signal generated by transcoder 12 to indicate an alarm condition.

As described above, the operation of transcoder 12 may be monitored by a local terminal or a remote terminal via modem connection block 86. Also shown is an RS-232 link for connecting co-located transcoder devices linked in a daisy chain.

Additional control inputs to transport encoder 12 include manually configurable selection/switches located on the panel, and control and configuration parameters of a Network Management System (NMS). As is known in the art, an NMS is a serial link that operates under the Simple Network Management Protocol (SNMP). N is also provided between the local transport coder and the remote transport coder^*An add/drop link (add/drop link) of 64 kilobits/second.

Fig. 3 is a functional block diagram of a simplified transcoder 12. Since the circuit performs different functions depending on whether it is desired to compress or decompress the E1 signal, fig. 3 provides an overview of the associated circuits contained in fig. 4 and 5, which are described below in fig. 4 and 5, and discuss the operation of each circuit block in more detail.

Referring to fig. 3, input/output circuitry (IO)90 is used to provide physical connections for incoming and outgoing E1 signals. Input/output circuit 90 may also provide functions such as impedance matching to meet any interface requirements. The input/output circuit 90 is connected to the non-compressed double base group circuits UD _1 to UD _ 492-98. A redundant non-compressed double base cluster circuit UD _ R100 is also connected to input/output circuit 90, and in the event of a failure of any of UD _1 through UD _492-98, UD _ R100 may switch in any incoming non-compressed E1 signal. The uncompressed double-basis-group circuits 92-100 may each include an Echo Cancellation Circuit (ECC)102 and 110. The uncompressed double-base-group circuits 92-100 are also connected to a compression/expansion circuit C/E _ a 120 and its redundant replica C/E _ B122. The compression/expansion circuits 120 and 122 implement a compression or expansion function. During normal operation, one of the compression/expansion circuits C/E _ A120 or C/E _ B122 is designated as the active circuit and the other is designated as the standby circuit. When a fault occurs, the standby working circuit is immediately changed into the active circuit.

The compressed data circuit CD _ a 126 and its redundant copy CD _ B128 are connected to the compression/expansion circuits 120 and 122. The compressed data circuits 126 and 128 either incorporate the compressed data into the available bandwidth of the compressed E1 signal or extract the embedded voice/data and control and signaling information from the compressed E1 signal. The CD processor 129 is located in the compressed data circuits 126 and 128. The CD processor 129 provides real-time traffic information, for example, every 16 milliseconds. The CD processor 129 may also be instructed to insert a predetermined data pattern into a particular one of the E1 signals in order to verify circuit operation and isolate the fault in the transport encoder 12.

A second input/output circuit (IO)130 provides a physical connection for the outgoing or incoming compressed E1 signals CE _ ACTIVE and CE _ STANDBY. Input/output circuit 130 also provides line driver and isolation functions.

In the event of a catastrophic failure, such as a loss of power, the uncompressed E1 signal on UE _1A may be connected directly to the compressed E1 signal CE1_ ACTIVE through the switch 132. The conditions that allow the E1 signal to bypass include both compressed data circuits CD _ A126 and CD _ B128 failing; both the companding circuits C/E _ A120 and C/E _ B122 fail; total power loss (including any redundant power) to transcoder 12; and compressed data circuits 126 and 128 detect a loss of synchronization for a predetermined period. The remote transport encoder 40 is informed of the bypass condition with a predetermined number of E1 extra bits so that the remote transport encoder 40 recognizes the transmitted E1 signal as an uncompressed E1 signal.

Control circuits CONTROLLER _ a 134 and CONTROLLER _ B136 provide communication and control between all functional circuits via a control bus 138. The control bus 138 includes a data bus, an address bus, and control lines. Control circuits 134 and 136 select control and/or communication targets using control lines and select specific locations within target circuits using address buses. The watchdog timer may be used to continue monitoring the operation of the control circuits 134 and 136. If a fault is detected in one of the control circuits, the watchdog timer is suspended to stop the operation of the active control circuit and to operate the redundant control circuit. The control circuits 134 and 136 may also communicate control parameters to the echo canceller (ECC)102 and 110 via an additional bus. The control circuits 134 and 136 also utilize a panel 140, where the panel 140 has some visual alarm indicator, such as an LED or alphanumeric display, and an RS232 that connects the local and remote terminals and any co-located transmission encoders. The manual control 142 also provides user input to drive menus for entering transport encoder controls and operating parameters.

The CDC bus 146 transfers signaling and additional signals between the uncompressed double-radix circuits 92-100 and the compressed data circuits 126 and 128. Each non-compressed double-radix circuit 92-100 sends an analysis of its incoming non-compressed E1 channel to the compressed data circuits 126 and 128 to be used to combine data from all incoming channels.

Referring to fig. 4, a compressed data path is shown from the uncompressed double-radix circuit 92 to the compression/expansion circuit 120 and then to the compressed data circuit 128. In this direction, four E1 data streams are compressed into one E1 data stream, which is then sent to the transcoder 40. The uncompressed double-radix circuit 92 receives a 2.048Mb standard E1 signal that electrically conforms to the physical/electrical characteristics of the international telecommunications union CCITT recommendation g.703 hierarchy digital interface and has the frame format of the CCITT specification g.704 synchronous frame structure used at the primary and secondary structural levels. In accordance with ITU g.703 and g.704, the E1 signal has 32 slots. Timeslot 0 is designated to carry framing and control signals and timeslot 16 is designated to carry Common Channel Signaling (CCS) or Channel Associated Signaling (CAS). The remaining time slots are used to carry the user bearer channels.

The uncompressed double-base-constellation circuit 92 includes an E1 interface and framing circuit 160 that converts the received E1 signal from a bipolar format to a unipolar format and extracts a 64kb signal in time slots 1 through 32. If the time slot 16 is set for channel associated signaling, then the signaling information may also be extracted A, B (or A, B, C, D) by further processing the time slot 16. The performance of the E1 signal and the alarm condition are also monitored and the monitoring results are communicated to the control circuits 136 and 138 (fig. 3). The uncompressed double-basis-group circuit 92 also includes a discriminator 162 that analyzes the 31 channels for voice/data determination. The signal is further analyzed with a voice/data indication according to the type of activity.

An echo canceller 164 may optionally be used to provide echo cancellation for the voice channel. The uncompressed double-basis-group circuit 92 may be configured to operate with or without an echo canceller. In the voice channel, it is further determined when to "mute" for the DSI circuitry 166 to apply digital language interpolation (DSI) techniques. During "silence," the DSI algorithm determines the noise level on the line and provides the noise parameters to the compressed double-basis circuit 92 for transmission for eventual reconstruction of the "silence" at the remote transcoder 40.

In the case of voice-band data, it is determined whether the data rate is greater than a certain rate (e.g., 9.6 kb). This information is forwarded (via controller 134) to the compress/expand circuit 120 without compressing the data.

The uncompressed double-radix circuit 92 also determines whether the signal contains high speed data, such as 56kb or 64kb, in which case a clear text channel will be allocated to the incoming channel on compression E1

A multiplexed 2.048Mb data stream containing voice/data channels is provided from the uncompressed double-basis-group circuit 92 to the compression/expansion circuit 120. The controller 134 controls the operation of the compression/expansion circuit 120, which may compress 124(31 x 4) channels from 64kb to 40, 32, 24 or 16kb using Adaptive Differential Pulse Code Modulation (ADPCM) techniques compatible with CCITT g.721 and g.723. If the data rate is less than or equal to 9.6kb, then the signal is compressed using ADPCM compression 170 of 40 kb. The figure shows that the speech signal is compressed in the ADPCM function block 172. When DSI is used on the voice channel, delay is performed with delay buffer 174.

The compression level is fixed for a preselected designated channel, but dynamic for a channel set to automatic. The 8-bit PCM word for each channel is compressed into 5, 4, 3, or 2 bits as specified by the controller 134. For the purpose of speaking the channel to go through, no compression is performed and the 8-bit word is passed through compression/expansion circuit 120 without change. The compression/expansion circuit 120 may also implement timing synchronization and clock selection/generation.

The compressed channel from the compression/expansion circuit 120 is provided to a compressed data circuit 128. Channel merger 180 receives channels containing 16kb of greater bandwidth and merges them into the available bandwidth. The generator 182 generates a signaling channel. The Proprietary Communication Link (PCL) generator 184 also uses the information structure PCL channel from the uncompressed double base group circuit 92 and the control circuit 134. Finally, a Proprietary Data Link (PDL), additional channel and slot 0 are constructed with generator 186 and attached to the combined data. The binary signal is then converted to bipolar E1 for output by interface and framer 190. The details of the proprietary communication link and the proprietary data link will be described below.

Fig. 5 shows the expanded data path through the compressed data circuit 126, the compress/expand circuit 120, and the uncompressed double-radix circuit 92. In this direction, a single compressed E1 data stream is expanded into four separate E1 data streams, which are then sent to standard E1 devices such as D4 channel libraries.

In the expansion direction, the interface and framing circuit 200 of the packed data circuit 126 interfaces with the incoming packed E1 signal, converting it from bipolar format to unipolar format, and providing enhanced performance monitoring functions. After framing and additional decimation, the channel de-combiner 202 de-combines the channels and extracts the Proprietary Communication Link (PCL) data. The proprietary communication link data is provided to the processor 204, which evaluates the data. The transport encoder 12 is configured with this data structure and supplies necessary additional information (Sa4 bit, RAI bit, bandwidth, DSI noise parameter) to the uncompressed double-basis group circuit 92 (fig. 3) through the CDC bus 146. If the proprietary communication link data indicates that one or more signaling channels exist, the channel is also extracted, provided to the CAS processor 206 for processing, and the appropriate information/data is sent to the uncompressed double-radix circuit 92 via the CDC bus 146. The extracted additional channels are also provided to an additional processor 208 for processing. The compressed data circuit 126 extracts 120 embedded voice/data channels (or 124 in the absence of signaling) from the incoming compressed E1 and passes them to the compression/expansion circuit 120 for decompression. The multiplexed 8.192Mb/s data stream links the compressed data circuit 126 with the compression/expansion circuit 120 and contains 120 or 124 voice/data channels.

The compress/expand circuit 120 includes an expand circuit 210 that places each voice/data channel within an 8.912Mb/s data stream and expands them from 2, 3, 4, 5, or 8 bits to 8 bits with Bandwidth (BW) information provided by the compress data circuit 126. The expansion circuit 210 also divides the 30 sets of data (31 sets when signaling is not used) into one multiplexed 2.048Mb/s data stream and sends it to the appropriate uncompressed dual basis clusters circuit 92(UD _1 to UD _4 or UD _ R).

The uncompressed double-basis-group circuit 128 puts each 64kb channel into the 2.048Mb/s data stream received from the compression/expansion circuit 120. For each channel, DSI processor 216 performs any required permutation of DSI noise with the noise parameters provided by compressed data circuit 126 via CDC bus 146. In the case of CAS signaling, interface and framing circuit 218 constructs channel 16 of uncompressed E1 from either the a, b signaling or the a, b, c, and d signaling provided by compressed data circuit 126. Channel 0 (framed channel) is constructed from the additional information ALM bits including Sa4-Sa 8. The constructed and decompressed E1 signal is passed to input/output circuit 90 (fig. 3).

The operation of transport encoders 12 and 40 may be better understood with reference to fig. 6-8, which illustrate control, signaling, and mapping of the bearer channel between compressed and uncompressed E1 in fig. 6-8. Additional information from the E1 of the uncompressed E1 line needs to be passed through with a fixed bandwidth and the remote receive transmit encoder is constructed with a Proprietary Communication Link (PCL) to obtain the necessary information to reconstruct each E1 link at the remote end. In addition, if signaling is to be transmitted, then a fixed bandwidth is also allocated for this. In E1 transmission systems, two signaling modes are typically used: common Channel Signaling (CCS) and Channel Associated Signaling (CAS). Any one of the signaling modes may be provided. The construction of the compressed E1 signal depends on which signaling system is being used.

Referring to fig. 6, a diagram illustrates mapping of control, signaling, and bearer channels. It is noted that although fig. 6 shows specific time slots used to carry certain signals, such designations are by way of example and the principles of the invention are not limited to the specific images shown in the figures. In each E1 signal frame, there are 32 total time slots, labeled from TS0 to TS31, each with a bandwidth of 64 kb/s. The replacement frame of time slot 0(TS0) is always used for framing and additional information. The time slot 0 of the compressed E1 signal is used to carry frame alignment signals and other control signals, such as Cyclic Redundancy Check (CRC), Remote Alarm Indicator (RAI), and Sa_4-8A bit. The format of time slot 0 is the same as that of standard E1.

As shown in FIG. 6, information selected from the uncompressed E1 signal, slot 0 of UE1_ A through UE1_ D, may be mapped onto the Proprietary Communication Link (PCL) of compressed E1, CE1_ ACTIVE, and CE1_ STANDBY occupying slot 1. The proprietary communication link provides end-to-end configuration, control and monitoring functions including remote alarm indicators, bandwidth, DSI noise parameters, and proprietary data for high speed alarm and diagnostic reporting to remote transport encodersLink (PDL) bits. May selectively include Sa in the slot 31 or the last slot to which the fraction E1 applies_5-8Some additional bits of (a). For example, the signaling in slot 16 of uncompressed E1 is also mapped to slot 2 of compressed E1. Time slot 3031 is used to carry compressed data for four uncompressed E1 signals.

Referring to fig. 7, a more detailed illustration of the mapping of the proprietary communication link of the time slot 0 of the uncompressed E1 signal to the compressed E1 signal is shown. The proprietary communication link is constructed in a multi-frame format where a certain number of frames carry channel bandwidth information (BW), idle noise parameters of DSI (N1-N3), Sa for uncompressed E1 signals₄Bits (datalink bits), Remote Alarm Indicator (RAI), and Proprietary Datalink (PDL) bits for high speed alarm/status/control. The PDL may have a multi-frame structure for carrying signaling information, software download control and status, and operation control, alarms and status of various circuit components. Since Sa can be as suggested by CCITT₄The bit serves as a message-based data link for operation, maintenance and performance monitoring, so end-to-end transparency to the bit is provided. This bandwidth may be used for other purposes when there is no need to transmit the Sa4 bits in uncompressed E1. Also, RAI end-to-end transparency is provided. The performance information of each uncompressed E1 may be communicated to the remote transport encoder in certain frames of the proprietary communication link. As shown, if end-to-end transparency is required, Sa of uncompressed E1 may also be selectively carried in the last slot used in slot 31 or partial E1 applications_4-8A bit.

Fig. 8 illustrates the mapping of the associated signaling to compression E1. In E1, the 16-frame structure of slot 16 is used for channel associated signaling. The signaling of four uncompressed E1 is mapped to one slot of compressed E1, e.g., slot 2. All 120(30 x 4) pieces of signaling for the incoming uncompressed E1 channel are supported with selected time slots in a 32-frame format, with signaling updated every 4 milliseconds. If more than two signaling bits have to be transmitted, such as a, b, c, and d per channel, the update rate in the 64-frame format is 8 milliseconds.

In the worse case of using associated channel signaling, the rest will be28 slots (32-3) are used for voice/voiceband data, assuming that no other 64kb/s channel through which clear text passes has been specified in advance. With 120 active voice channels, the required ADPCM compression is from 8 bits to 1.87 bits (28)^*8/120). With DSI providing additional bandwidth gain, ADPCM compression can provide a speech quality of 24kb/s ADPCM for all channels.

The signaling information in the common channel signaling is passed through the compression E1 unchanged. The time slots from UE1_ a to UE1_ D carrying common channel signaling (typically time slot 16) are mapped to predetermined time slots from TS _ a to TS _ D in compact E1. If it is not required that all four non-compressed E1 be used to pass common-path signaling, the system architecture will only allow the designated non-compressed E1 to pass signaling. For example, if only the UE1_ D is to be over common-path signaling, TS _ D on E1 is compressed to carry signaling information, while TS _ a through TS _ c are used for voice/data communications. Thus, as constructed by the control software, the TS2-TS30 may be allocated to voice/data communications in a dynamic or pre-allocated manner. Any unused TS _ a, TS _ b, TS _ c, TS _ d may be used for dynamic allocation of voice/data traffic.

In a worse case, if all of the fixed bandwidth described above is required, it leaves 25 slots (32-7) for the voice/speech band data, assuming that the 64kb/s channel through which the clear text passes is not pre-specified. The pre-assigned pass through (64kb/s) channel directly reduces the number of slots available for voice/voice band data in compression E1.

Transcoder 12 may compress the incoming voice and/or uncompressed E1 data channels using a combination of ADPCM and DSI techniques. The 8 bit PCM encoded samples are compressed into 5, 4, 3 or 2 bits, respectively, forming a stream of 40, 32, 24 or 16kb ADPCM. No frames containing speech energy are used in DSI applications so that the speech transmission is not subject to clipping, which can sometimes be found in pure DSI applications.

The transcoder 12 of the present invention supports the part E1 application. The bandwidth that can be used on compression E1 can be set by the "available BW" parameter, the following is an example:

1.32 → use all (0-31)64kb channels; this is the default setting;

2.24 → only the 64kb channels of 0-23 are used; and

3.16 → only 64kb channels of 0-15 are used.

The "available BW" parameter may have any value from 4 to 32. When the "available BW" parameter is less than 32, any unused channels of compression E1 may be filled with a predetermined pattern.

After all fixed and pre-allocated channel bandwidths have been allocated, the remaining channels are automatically allocated to incoming channels in the best possible way, depending on the communication conditions. As discussed above, the available bandwidth for dynamic allocation may also be limited to support fractional E1 applications. The total bandwidth available on the compact E1 link may be defined as 16, 24, or 32 (default) channels of 64kb bandwidth. In the partial E1 application case, if the system is so constructed, the last channel of available bandwidth may carry Sa5-8, which is additional to all non-compressed E1.

Voice/data (V/D) channels contain bandwidth that can be automatically dynamically allocated to incoming channels or manually pre-allocated to certain incoming channels. In some applications, such as high data rate situations greater than 56kb, a dedicated 64kb channel must be pre-allocated. Each allocation uses 8-bit words and no DSI. The following table illustrates a bandwidth allocation scheme for compression E1. A. B … is an 8-bit pattern transferred in the PCL represented by the bandwidth allocation structure.

Compression of bandwidth allocation of E1
									Control structure (PCL)	Average bandwidth	Signaling options	By additional information	TS_a	TS_b	TS_c	TS_d	Other time slots
A	32	CAS:ab	Whether or not	32 frame CAS	V/D	V/D	V/D	V/D
									B	32	CAS:ab	Is that	32 frame CAS	V/D	V/D	V/D	V/D; TS 31: additional information
C	32	CAS:abcd	Whether or not	64-frame CAS	V/D	V/D	V/D	V/D
									D	32	CAS:abcd	Is that	64-frame CAS	V/D	V/D	V/D	V/D; TS 31: additional information
E	32	CCS:ALL	Whether or not	CCS-A	CCS-B	CCS-C	CCS-D	V/D
									F	32	CCS:ALL	Is that	CCS-A	CCS-B	CCS-C	CCS-D	V/D; TS 31: additional information
G	24	CAS:ab	Whether or not	32 frame CAS	V/D	V/D	V/D	To TS 23: V/D

H	24	CAS:ab	Is that	32 frame CAS	V/D	V/D	V/D	V/D; TS 23: additional information
									I	24	CAS:abcd	Whether or not	64-frame CAS	V/D	V/D	V/D	To TS 23: V/D
J	24	CAS:abcd	Is that	64-frame CAS	V/D	V/D	V/D	V/D; TS 23: additional information
									K	24	CCS:ALL	Whether or not	CCS-A	CCS-B	CCS-C	CCS-D	To TS 23: V/D
L	24	CCS:ALL	Is that	CCS-A	CCS-B	CCS-C	CCS-D	V/D; TS 23: additional information
									M	16	CAS:ab	Whether or not	32 frame CAS	V/D	V/D	V/D	To TS 15: V/D
N	16	CAS:ab	Is that	32 frame CAS	V/D	V/D	V/D	V/D; TS 15: additional information
									O	16	CAS:abcd	Whether or not	64-frame CAS	V/D	V/D	V/D	To TS 15: additional information
P	16	CAS:abcd	Is that	64-frame CAS	V/D	V/D	V/D	V/D; TS 15: additional information
									Q	16	CCS:ALL	Whether or not	CCS-A	CCS-B	CCS-C	CCS-D	To TS 15: V/D
R	16	CCS:ALL	Is that	CCS-A	CCS-B	CCS-C	CCS-D	V/D; TS 15: additional information
									S	32	Is free of	Whether or not	V/D	V/D	V/D	V/D	To TS 31: V/D
T	32	Is free of	Is that	V/D	V/D	V/D	V/D	V/D; TS 31: additional information
									U	24	Is free of	Whether or not	V/D	V/D	V/D	V/D	To TS 23: V/D
V	24	Is free of	Is that	V/D	V/D	V/D	V/D	V/D; TS 23: additional information

W	16	Is free of	Whether or not	V/D	V/D	V/D	V/D	To TS 15: V/D
									X	16	Is free of	Is that	V/D	V/D	V/D	V/D	V/D; TS 15: additional information

Thus, depending on the bandwidth configuration, a channel between 30 and 25 may be used for voice/data communication between the two transport encoders. These channels allocate contiguous bandwidth to incoming calls. The user may set the maximum data call allowed by the "data" parameter. The data call is automatically allocated 40kb or 64kb of bandwidth as determined by call parameters, such as integer rate, which are automatically detected by hardware resident on uncompressed dual-basis group circuit 92 (fig. 3). Once a particular bandwidth is allocated to a data call, it remains fixed for the duration of the call. All voice calls and any data calls that exceed the allowed maximum are compressed into the remaining bandwidth with the DSI application software.

In some applications, certain channels may be blocked to normal traffic. This feature is useful when some common channel signaling channels are to be passed. For example, if only the UE1_ a needs to pass its associated signaling and block the remaining common channel signaling channels associated with the UE1_ B through UE1_ D, then the option of "no" signaling may be selected and the common channel signaling channel allocated to the clear channel on compression E1. Clear text (64kb) or zero (0kb) bandwidth may be pre-allocated to any one of the incoming 124 channels.

The predetermined bit of the PCL may be used to update the controller 134 firmware in the remote transport encoder 40 (fig. 3) over the compressed E1 link. For example, the dedicated data link bit (Sa) may be temporarily set₄) The bits used for software download. The download is initiated by the controller 134 software and controlled and monitored at the remote unit by the PDL.

The maximum number of data channels determined by the user via the "data" parameter supports voice, voice-band data, and high-speed data channels. A specific bandwidth is automatically allocated to all data channels according to the rate of the data channels, and all data channels are not subject to DSI. However, once the data channel (high speed and dial) is equal to the "data" parameter, the additional data channel undergoes the same compression as the voice channel.

Comprehensive traffic statistics are provided for all channels that are dynamically allocated bandwidth. Statistical calculations and updates are performed periodically. A local or remote terminal coupled to transcoder 12 may display the calculated statistics at set time intervals. A statistical record of the predetermined number of days may be maintained in the memory of the controller 134. Statistical monitoring and computation of channel activity, bit rate, congestion, and voice/data with reduced data rate.

In order to achieve proper operation, the transmission of information between the local and remote transport encoders 12 and 40 (FIG. 1) must be properly synchronized. The master/slave synchronization strategy specifies that one unit is the master and the other is the slave, where the slave unit extracts the timing from the received compressed E1. The master unit may extract timing from any given source, including external and internal reference clock signals. Thus, sending compressed E1 originates from the system clock, while sending uncompressed E1 originates from the system clock or cycle timing option. Daisy-chained co-located transcoder transmissions can use SYNC _ IN and SYNC _ OUT to get synchronization from a single source.

It can be seen that although the transcoder and compression E1 of the present invention has been described with a4 to 1 (4: 1) compression ratio, a compression ratio of N: 1, where N is greater than 1, can be achieved without undue experimentation. The compression ratio may be selected based on available bandwidth and implementation application capabilities and practical capabilities.

Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims (23)

1. An N: 1E 1 compression method, comprising the steps of:

receiving N incoming E1 signals;

extracting a plurality of voice/data channels from said N incoming E1 signals;

extracting control, monitoring and status information channels from the N incoming E1 signals;

compressing the data in the extracted voice/data channel;

generating and incorporating control, monitoring and status information into a predetermined channel of a compressed E1 signal; and is

The compressed data is incorporated into the available channels of the compressed E1 signal.

2. The N: 1E 1 compression method of claim 1, further comprising the steps of:

distinguishing a channel carrying voice service from a channel carrying data service; and is

In response, the data is compressed.

3. The N: 1E 1 compression method of claim 1, further comprising the steps of;

distinguishing channels carrying high-speed data; and is

Data carried in the high speed channel is not compressed.

4. The N: 1E 1 compression method of claim 1, wherein the combining step further comprises combining selected data into pre-allocated channels in the compressed E1 signal.

5. The N: 1E 1 compression method of claim 1, wherein the merging step comprises the steps of:

the compressed data is combined into a predetermined number of channels to support portion E1, the predetermined number being less than the number of available channels.

6. The N: 1E 1 compression method of claim 1, wherein the data compression includes the steps of;

determining an available bandwidth; and is

Compressing the data at a highest rate in response to the available bandwidth.

7. The N: 1E 1 compression method of claim 1, further comprising the steps of;

echo cancellation is performed on the selected channel.

8. The N: 1E 1 compression method of claim 1, wherein the step of incorporating further comprises the step of incorporating signaling information into the compressed E1 signal.

9. The N: 1E 1 compression method of claim 8, wherein the step of combining signaling information includes the step of combining common channel signaling information into at least one predetermined channel of the compressed E1 signal.

10. The N: 1E 1 compression method of claim 8, wherein the step of combining signaling information includes the step of combining associated signaling information into at least one predetermined channel of the compressed E1 signal.

11. The N: 1E 1 compression method of claim 1, wherein the step of incorporating further comprises the step of incorporating the selected control, monitoring and status information into at least one predetermined channel.

12. The N: 1E 1 compression method of claim 11, wherein the merging step further comprises the step of merging selected control, monitoring and status information into a proprietary communication link.

13. The N: 1E 1 compression method of claim 11, wherein the step of combining further comprises the step of combining bandwidth information for each compressed data channel into the predetermined channel.

14. The N: 1E 1 compression method of claim 11, wherein the data compression step further includes the step of digital language interpolation, and the combining step further includes the step of combining noise parameters for digital language interpolation into the predetermined channel.

15. An N: 1E 1 compression method as claimed in claim 11, wherein the step of incorporating further includes the step of incorporating alarm information into the predetermined channel.

16. The N: 1E 1 compression method of claim 11, wherein the step of incorporating further comprises the step of incorporating a remote alert indicator into the predetermined channel.

17. The N: 1E 1 compression method of claim 11, wherein the merging step further comprises compressing Sa₄Is incorporated into the predetermined channel so as not to change the Sa₄A bit, a step of transmitting it to a remote transmission encoder.

18. The N: 1E 1 compression method according to claim 11, wherein the combining step further comprises combining Sa's in the predetermined channels_5-8So that the bits are transmitted to the remote transmission encoder without being changed.

19. The N: 1E 1 compression method of claim 11, wherein the merging step further comprises the step of merging data link bits into the predetermined channel so that the data link bits are transmitted to a remote transport encoder without changing the data link bits.

20. The N: 1E 1 compression method of claim 11, wherein the merging step further comprises the step of merging proprietary datalink bits into the predetermined channel with control, alarm and transport coder state information operations.

21. The N: 1E 1 compression method of claim 11, wherein the proprietary data link bit merging step further comprises the step of merging operational information of the selected system parts.

22. The N: 1E 1 compression method of claim 11, wherein the step of incorporating further comprises the step of incorporating downloaded software of a remote transport encoder and its control and status information into the predetermined channel.

23. The N: 1E 1 compression method of claim 1, wherein the merging step further comprises the steps of:

merging high-speed data into the compressed signal without compression;

combining dedicated voice/data channels into pre-allocated channels; and is

Compressed data is dynamically allocated and combined in available channels.