A Clear Channel circuit is a TDM-type point-to-point leased circuit based on multiplexing multiple n X 64kbps data channels and deploying them on any standard interface.

Internetghana's Clear Channel is a nailed circuit solution which guarantees a dedicated Bandwidth of n x 64kbps. It is significant to note that the bandwidth is dedicated end-to-end, which means that the minimum bandwidth of 64kbps cannot be compromised under any circumstance.

Unlike some solutions where the more clients there are on the central system, the less bandwidth throughput for a typical client, Internetghana's Clear Channel solution guarantees a dedicated channel for any client without recourse to how many clients are on the network.

In a typical case scenario where a provider is operating from a base station with a total throughput of 10mbps, a single client on the remote end may be assured of a dedicated bandwidth of say 128kbps as long as other clients do not come on the service to compete with or share in the total Bandwidth allocation from the base station. The client’s throughput logically depreciates when for instance about 30 clients come on the service with all of them requiring 128k or more.



THE SOLUTION

The solution is based on TDM-based IAD (Integrated Access Device Service) products for solely Data circuits.
The basic component of a Clear channel circuit is an E1 or fractional E1 Access IAD Unit. This unit is used as an integrating multiplexer for E1 and fractional E1 services.
The unit has two data ports with selectable synchronous data rates for any multiple of 64Kbps, up to 1,984kbps, main E1 port with an internal LTU for termination of E1 service from E1 Networks and a sub-E1 drop-and-insert port. Timeslot assignment is programmable, allowing data from each data port and from the sub-E1 port to be placed into timeslots on the main link, either consecutively or alternately.

Standard E1/T1 frames divide the bandwidth into timeslots - 24 for T1 and 30 for E1. The IAD integrates the data traffic by assigning each to dedicated pre-programmed timeslots. The integrated E1/T1 link is routed through a digital cross connect (DACS) residing in Internetghana's point-of-presence (POP). The DACS separates the data traffic and routes them to the appropriate backbone network.
Clear channel systems offer selectable data channel timing MODES. There are three timing modes. The first timing mode provides transmit and receive clocks for the user equipment connected to the data port of the TDM MUX.

In the second timing mode the data channel sends the receive data accompanied by the receive clock derived from the main system clock to the user’s equipment connected to the data port of the TDM MUX, and accepts user’s data according to the user’s equipment transmit clock.
In the third timing mode the data channel transmits and receives data according to the clock signal provided by the equipment connected to the data port of the TDM MUX.
When using this clocking mode, the main link timing must be locked to the clock signal supplied by the user’s data port Interface. These multiple clock source selection ensures maximum flexibility, Both for the main link and for the data ports, enabling the support of different applications of Internetghana’s Clear Channel solution. MORE

The figure below shows how timeslots are assigned to frames and dedicated to data channels.


Fig:1 Allocation of time slots to data channels