APPARATUS AND METHOD FOR MAPPING E1 TELECOMMUNICATIONS SIGNALS ONTO A SUBSCRIBER BUS

Abstract: In a subscriber loop equipment (10) having a subscriber bus (26), there is provided an odd data stream carrying a first set of data time slots of an E1 signal and a first set of signaling and control time slots of the E1 signal, and an even data stream carrying a second set of data time slots of the E1 signal and a second set of signaling and control time slots of the E1 signal. The odd and even data streams are bit-interleaved and transported on the subscriber bus (26).

Description: APPARATUS AND METHOD FOR MAPPING El TELECOMMUNICATIONS SIGNALS ONTO A SUBSCRIBER BUS TECHNICAL FIELD OF THE INVENTION This invention is related in general to the field of telecommunications systems. More particularly, the invention is related to apparatus and method for mapping telecommunications signals onto a subscriber bus. BACKGROUND OF THE INVENTION In the early days of telecommunication, a copper wire medium was used to carry a single information channel. Because the greatest proportion of cost is in the materials and construction of the physical link, telephony engineers have developed ways to pack multiple channels onto a single physical link. Frequency division multiplexing (FDM) and time division multiplexing {TDM) have been devised to multiplex multiple streams of analog and pulse code modulation (PCM) digital signals, respectively, into one. For digital signals, the time division multiplexing hierarchy is DSO through DS4, where a DSO is a single 0.064 Mbps channel, a DS1 is 24 DSOs multiplexed together, and a DS4 is 4,032 DSOs multiplexed together. A similar time division multiplexing scheme is used in international telephone systems based on 32 -channel format, where each channel is occupied by a DSO signal. The international digital systems, based on International Telecommunication Union CCITT's G.700 Series Recommendations, are commonly called El or CEPT-1. The El signals are based on blocks of 32 channels or time slots, of which time slot 0 and time slot 16 are typically used for control and signaling, respectively. American telecommunications equipment manufacturers desiring to compete in the international arena must design and produce equipment that operate under the international standard. Alternatively, in order to achieve compatibility, telecommunications equipment which were originally designed and manufactured to handle signals under the American standards must be modified to accommodate international signals. SUMMARY OF THE INVENTION Accordingly, there is a need to provide subscriber loop equipment that are compatible with international standards, such as the transport of the El signal. In one aspect of the invention, in a channel bank having a subscriber bus having a thirty-two time slot frame, there is provided an odd data stream carrying a first set of data time slots of an El signal and a first set of signaling and control time slots of the El signal, and an even data stream carrying a second set of data time slots of the El signal and a second set of signaling and control time slots of the El signal. The odd and even data streams are bit-interleaved and transported on the subscriber bus. In another aspect of the invention, a method for mapping El signals onto a subscriber bus includes the steps of mapping a first set of data channels of the El signals onto predetermined time slots of a first data stream, and mapping a first set of signaling and control channels of the El signals onto other predetermined time slots of the first data stream. Further included are the steps of mapping a second set of data channels of the El signals onto predetermined time slots of a second data stream, and mapping a second set of signaling and control channels of the El signals onto other predetermined time slots of the second data stream. BRIEF DESCRIPTION OF THE DRAWINGS For a better understanding of the present invention, reference may be made to the accompanying drawings, in which : FIGURE 1 is a top level block diagram of an exemplary channel bank unit constructed according to the teachings of the present invention; FIGURE 2 is a diagram of an embodiment of a subscriber bus structure according to the teachings of the present invention; FIGURES 3A and 3B are exemplary mapping diagrams for the subscriber bus; and FIGURES 4A and 4B are further exemplary mapping diagrams for the subscriber bus . DETAILED DESCRIPTION OF THE INVENTION The preferred embodiment (s) of the present invention is (are) illustrated in FIGURES 1-4, like reference numerals being used to refer to like and corresponding parts of the various drawings. Referring to FIGURE 1, a channel bank 10 constructed according to the teachings of the present invention is shown. Channel bank 10 is coupled to a digital loop carrier 12 through a data and control message link 14. Digital loop carrier 12 is in communications with equipment residing in a central office (not shown) , such as a central office terminal (not shown) of the digital loop carrier and a digital cross-connect system (not shown) . Channel bank 10 is a DSO to DS1 or DSO to El multiplexing equipment primarily used for analog voice to pulse code modulation (PCM) conversion and multiplexing. Channel bank 10 includes a bank control unit (BCU) 20, which may be coupled to more than one channel unit (CU) 22 via a subscriber bus 26. Channel units 22 may operate at DS1 and DS3 rates, as well as international rates such as El. A plurality of subscriber equipment 30 may be coupled to each channel unit 22. The data carried on subscriber bus 26 has the exemplary format shown in FIGURE 2. Each frame includes 32 time slots or channels, eight of which are reserved or devoted to signaling and control. In FIGURE 2, "R" denotes a reserved slot; "SI" through "S4" denote signaling time slots; "F" denotes framing; "SR" denotes systems communications service request channel; and "DL" denotes data link. In the signaling time slots of each frame, the arrows indicate the signaling time slots for the channels. The word structure for each time slot is also shown. Subscriber bus 26 is comprised of two bit-interleaved data streams. FIGURES 3A and 3B show the data and signaling format for the ODD and EVEN data streams, which may be identical to transport two DS1 signals . Note that "sig" denotes signaling time slots. The dual DS1 or TI mapping scheme is described in copendmg U.S. Patent Application titled Appara tus and Method for Mapping Tel ecommuni ca tions Signals onto a Subscriber Bus , Serial No. , filed on . To accommodate El signals, two data streams are need to transport the data and signaling of one El signal, since it is comprised of 32 data time slots. The exemplary format for transporting the El signal by the ODD and EVEN data streams of a subscriber bus is shown in FIGURES 4A and 4B. Alternatively, the El signal may be transported on two odd data streams of two subscriber buses. It may be seen that the channels are split between the two data streams. In the embodiment shown in FIGURES 4A and 4B, 24 channels are carried on the ODD data stream, and the remaining eight channels are carried on the EVEN data stream. It may be seen that the exact mapping of the El channels onto the data streams may differ than shown. Further, it is contemplated that more than two data streams may be multiplexed together to form subscriber bus 26. 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 therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims: WHAT IS CLAIMED IS: 1. In a channel bank having a subscriber bus having a thirty-two time slot frame, comprising: an odd data stream carrying a first set of data time slots of an El signal and a first set of signaling and control time slots of the El signal; an even data stream carrying a second set of data time slots of the El signal and a second set of signaling and control time slots of the El signal; and the odd and even data streams being bit -interleaved and transported on the subscriber bus . 2. The channel bank, as set forth in claim 1, wherein the odd data stream comprises data time slots 1-3, 5-7, 9-11, 13-15, 17-19, 21-23, 25-27, and 29-31. 3. The channel bank, as set forth in claim 1, wherein time slots 1-3, 5-7, 9-11, 13-15, 17-19, 21-23, 25-27, and 29-31 of the odd data stream comprises data time slots 1-3, 5-7, 9-11, 13-15, 17-19, 21-23, 25-27, and 29-31, respectively. 4. The channel bank, as set forth in claim 1, wherein the even data stream comprises data time slots 0, 4, 8, 12, 16, 20, 24, and 28. 5. The channel bank, as set forth in claim 1, wherein time slots 1, 5, 9, 13, 17, 21, 25, and 29 of the even data stream comprises data time slots 0, 4, 8, 12, 16, 20, 24, and 28, respectively. 6. The channel bank, as set forth in claim 1, wherein the odd data stream comprises signaling and control time slots SRQ and DL. 7. The channel bank, as set forth in claim 1, wherein time slots 16 and 24 of the odd data stream comprises signaling and control time slots SR and DL, respectively. 8. The channel bank, as set forth in claim 1, wherein the odd data stream comprises signaling time slots S1-S4. 9. The channel bank, as set forth in claim 1, wherein time slots 4, 12, 20, and 28 of the odd data stream comprises signaling time slots S1-S4, respectively. 10. The channel bank, as set forth in claim 1, wherein the even data stream comprises signaling time slots S1-S4. 11. The channel bank, as set forth in claim 1, wherein time slots 4, 12, 20, and 28 of the even data stream comprises signaling time slots S1-S4, respectively. 12. A subscriber loop equipment having a bus, comprising : an odd data stream carrying data time slots 1-3, 5-7, 9-11, 13-15, 17-19, 21-23, 25-27, and 29-31 of an El signal and a first set of signaling and control time slots of the El signal; an even data stream carrying data time slots 0, 4, 8, 12, 16, 20, 24, and 28 of the El signal and a second set of signaling and control time slots of the El signal; and the odd and even data streams being bit -interleaved and transported on the bus. 13. The subscriber loop equipment, as set forth in claim 12, wherein time slots 1-3, 5-7, 9-11, 13-15, 17-19, 21-23, 25-27, and 29-31 of the odd data stream comprises data time slots 1-3, 5-7, 9-11, 13-15, 17-19, 21-23, 25-27, and 29-31, respectively. 14. The subscriber loop equipment, as set forth in claim 12, wherein time slots 1, 5, 9, 13, 17, 21, 25, and 29 of the even data stream comprises data time slots 0, 4, 8, 12, 16, 20, 24, and 28, respectively. 15. The subscriber loop equipment, as set forth in claim 12, wherein the odd data stream comprises signaling and control time slots SRQ and DL. 16. The subscriber loop equipment, as set forth in claim 12, wherein time slots 16 and 24 of the odd data stream comprises signaling and control time slots SRQ and DL, respectively. 17. The subscriber loop equipment, as set forth in claim 12, wherein the odd data stream comprises signaling time slots S1-S4. 18. The subscriber loop equipment, as set forth in claim 12, wherein time slots 4, 12, 20, and 28 of the odd data stream comprises signaling time slots S1-S4, respectively . 19. The subscriber loop equipment, as set forth in claim 12, wherein the even data stream comprises signaling time slots S1-S4. 20. The subscriber loop equipment, as set forth in claim 12, wherein time slots 4, 12, 20, and 28 of the even data stream comprises signaling time slots S1-S4, respectively. 21. A method for mapping El signals onto a subscriber bus having thirty-two time slot frames, comprising the steps of : mapping a first set of data channels of the El signals onto predetermined time slots of a first data stream; mapping a first set of signaling and control channels of the El signals onto other predetermined time slots of the first data stream; mapping a second set of data channels of the El signals onto predetermined time slots of a second data stream; mapping a second set of signaling and control channels of the El signals onto other predetermined time slots of the second data stream; and bit interleaving the first and second data streams. 22. The method, as set forth in claim 21, wherein the first set of El data channels mapping step comprises the step of mapping data channels 1-3, 5-7, 9-11, 13-15, 17-19, 21-23, 25-27, and 29-31 onto the predetermined time slots of the first data stream. 23. The method, as set forth in claim 21, wherein the first set of El data channels mapping step comprises the step of mapping data channels 1-3, 5-7, 9-11, 13-15, 17-19, 21-23, 25-27, and 29-31 onto time slots 1-3, 5-7, 9-11, 13- 15, 17-19, 21-23, 25-27, and 29-31, respectively, of the first data stream. 24. The method, as set forth in claim 21, wherein the second set of El data channels mapping step comprises the step of mapping data channels 0, 4, 8, 12, 16, 20, 24, and 28 onto the predetermined time slots of the even data stream. 25. The method, as set forth in claim 21, wherein the second set of El data channels mapping step comprises the step of mapping data channels 0, 4, 8, 12, 16, 20, 24, and 28 onto time slots 1, 5, 9, 13, 17, 21, 25, and 29, respectively, of the second data stream. 26. The method, as set forth in claim 21, wherein the first set of signaling and control channel mapping step comprises the step of mapping an SRQ and a DL signaling channels onto the other predetermined time slots of the first data stream. 27. The method, as set forth in claim 21, wherein the first set of signaling and control channel mapping step comprises the step of mapping an SRQ and a DL signaling channels onto time slots 16 and 24 of the first data stream. 28. The method, as set forth in claim 21, wherein the first set of signaling and control channel mapping step comprises the step of mapping S1-S4 signaling channels onto the other predetermined time slots of the first data stream. 29. The method, as set forth in claim 21, wherein the first set of signaling and control channel mapping step comprises the step of mapping S1-S4 signaling channels onto time slots 4, 12, 20, and 28, respectively, of the first data stream. 30. The method, as set forth in claim 21, wherein the second set of signaling and control channel mapping step comprises the step of mapping S1-S4 signaling channels onto the other predetermined time slots of the second data stream. 31. The method, as set forth in claim 21, wherein the second set of signaling and control channel mapping step comprises the step of mapping S1-S4 signaling channels onto time slots 4, 12, 20, and 28, respectively, of the second data stream.

Inventors: DESCHAINE STEPHEN A, ENTEZARI MANOUCHEHR, KLECKA RUDOLPH B III, DESCHAINE, STEPHEN, A., ENTEZARI, MANOUCHEHR, KLECKA, RUDOLPH, B., III
Applicants: DSC TELECOM LP, DSC TELECOM L.P.
Application year: 1997
Main classification: H04J3
IPC codes: H04J3, H04Q11