Method and apparatus for the interchanges of PCM word

• US 4,167,652 A
• Filed: 01/13/1978
• Issued: 09/11/1979
• Est. Priority Date: 10/17/1974
• Status: Expired due to Term

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Braugenhardt, Anders E. S., Anas, Johan O., Odhelius, Gustaf H. V., Hedin, Nils A.
• Primary Examiner(s): Stewart, David L.
• Application Number:
  US05/869,150
• Time in Patent Office: 606 Days
• Field of Search: 179/15 AQ, 179/15 AT, 179/15 AL
• US Class Current: 370/379
• CPC Class Codes: H04Q 11/06 Time-space-time switching

Abstract

An integrated switching and transmission of PCM words associated with channels and transferred on links utilizing the time-time switching principle is achieved by connecting an interhighway, i.e., a common time multiplex connection on which the PCM words are transferred in bus time slots, to inward and outward traffic memory arrangements each associated with one of the links. The memories store the words and in addition not only store, for each established connection channel, index numbers indicating the actual incoming and outgoing channel, but also a time index number indicating which bus time slot during an index read out phase is used for the connection. The phases are introduced in order to avoid the necessity of using memory access times corresponding to the bus time slots. Each phase comprises a number of bus time slots and each frame of the PCM words includes at least so many such phases as there are channels on each link. The stored channel and time index numbers are read by means of a regular scanning at a frequency defined by the phases. By means of the channel index numbers irregular sequences are achieved for the PCM words according to the established connections. By means of the time index number read during the respective phase the actual PCM word is transferred to and from the interhighway.

Claims

1. The method of integrated switching and transmission of PCM words which are incoming and outgoing on links each link having a plurality of channels, each channel being associated with a link time slot in a link frame, the switching being carried out by means of an interhighway bus acting as a common time multiplex connection on which the PCM words are transferred in bus time slots, the interhighway connected between inward traffic memory means, each associated with one incoming link, and outward traffic memory means, each associated with one outgoing link, each of said traffic memory means including a PCM word memory and an index number memory, respectively, said method comprising the steps of storing in corresponding locations of the index number memories of the respectively inward and outward memory means associated with an established connection in which the respective link is involved a channel index number associated with the incoming channel and a channel index number associated with the outgoing channel of the connection as well as a time index number which is the same for the respective inward and outward memory means, writing cyclically the incoming PCM words into the PCM word memories of the inward memory means, respectively, by means of a regular scanning occurring at a frequency defined by the link time slots, reading cyclically the outgoing PCM words from the PCM word memories of the outward memory means, reading cyclically the channel and the time index numbers from the index number memories by means of a regular scanning occurring at a frequency defined by index read out phases, each index read out phase comprising a number of the interhighway bus time slots and each interhighway bus frame including at least as many index read out phases as there are link time slots in a link frame, reading the PCM words from the PCM word memory into a buffer of the respective inward memory means in an irregular sequence determined by means of the channel index numbers read from the index number memory of said inward memory means, transferring the PCM words of an actual connection from the buffer of said respective inward memory means via the interhighway bus to a buffer of the respective outward memory means under the control of the time index number associated with the connection and read from the index number memories of said inward and outward memory means, and writing into the PCM word memory the PCM words from the buffer in the respective outward memory means in an irregular sequence determined by means of the channel index numbers read from the index memory of said outward memory arrangement.

2. Method according to claim 1 wherein the number of channels is equal in incoming and outgoing links.

3. An exchange for integrated switching and transmission of PCM words which are received as incoming PCM words in incoming channels on at least one incoming link and sent out as outgoing PCM words in outgoing channels on at least one outgoing link, the channels being assigned link time slots in the links, the exchange comprising:

(a) an inward traffic word memory means, connected to the incoming link, for storing the incoming PCM words from the incoming link, said inward traffic word memory means having a plurality of indexed positions, each associated with a different one of the incoming channels of the incoming links;

(b) an outward traffic word memory means, connected to the outgoing link, for storing outgoing PCM words before transfer to the outgoing link, said outward traffic word memory means having a plurality of index positions, each associated with a different one of the outgoing channels of the outgoing link;

(c) an interhighway bus means connected to said inward and outward traffic word memory means and arranged as a time multiplex connection common for all PCM words wherein PCM words are transformed during assigned bus time slots;

(d) a timing generator means for producing a pulse frequency and multiples of the pulse frequency, wherein

the pulse frequency determines frames of the PCM words,

a first frequency multiple determines index read out times,

a second and a third frequency multiple determines link time slots during which the PCM words are transferred on the incoming and outgoing links, respectively, and

a fourth frequency multiple determines bus time slots during which the PCM words are transferred on the interhighway bus means, the fourth frequency multiple being a multiple of the first frequency multiple which is at least equal to the larger of the second and the third frequency multiple, said bus time slots being grouped into phases associated with the index read out times;

(e) inward traffic index memory means, associated with the incoming link, and outward traffic index memory means associated with the outgoing link, for storing in corresponding locations, in order to establish a connection in which the respective link is involved, a channel index number indicating the respective channel of the connection and a time index number allotted to the connection in order to determine which bus time slot within a phase is used on the interhighway bus means;

(f) inward traffic scanning means for controlling the writing of the incoming PCM words of the channels of the incoming link into the indexed positions of the inward traffic memory means associated with the channels, said inward traffic scanning means stepping in a fixed-cycle operation determined by said second frequency multiple;

(g) outward traffic scanning means for controlling the reading of the outgoing PCM words from the indexed positions of the outward traffic memory means to the association channels of the outgoing link, said outward traffic scanning means stepping in a fixed-cycle operation determined by said third frequency multiple;

(h) index scanning means for controlling the reading of the channel and time index numbers from said traffic index memory means, said index scanning means being stepped forward by a fixed-cycle operation determined by said first frequency multiple;

(i) a plurality of decoder means, each associated with a different one of the links, for decoding the channel index numbers read from the associated traffic index memory means in order to access the associated inward traffic word memory means for reading out the PCM word stored in the indexed position associated with the decoded incoming channel index number and the associated outward word traffic memory for making available the index position associated with the decoded outgoing channel index number for receiving and storing a PCM word, respectively;

(j) an inletting means associated with the incoming link and having an input connected to the inward traffic memory means and an output connected to the interhighway bus means for transferring PCM words thereto in bus time slots which are determined by the time index numbers; and

(k) an outletting means associated with the outgoing link and having an input connected to the interhighway bus means and an output connected to the outward traffic memory means for accepting the PCM words from the interhighway bus means in bus time slots which are determined by the time index numbers for subsequent transfer to the outward traffic memory means.

4. The exchange according to claim 3, wherein the timing generator means produces second and third frequency multiples which are equal.