Telcos could have a massive advantage in upstream speed. Sckipio is confident they will deliver an efficient way to switch bandwidth. I want upstream. Jennie does video and we upload terabytes to Amazon's unlimited cloud. My neighbor probably prefers downstream.
This "dynamic time slot allocation" (DTA) demonstrated by Adtran worked over coax. No vectoring is needed because the shielding minimizes any crosstalk. Calix has previously shown G.fast over coax. The engineers are confident they will soon be able to deliver 750 up, 750 down on coax. Their companies have promised that to AT&T, which acquired coax systems with DirecTV.
Vectoring a DTA system in typical telco multi-line binders is much more challenging.
The calculations to vector at 500+ megabits are demanding. Switching upstream and downstream dynamically adds complexity. A British Telecom engineer suggested DTA wasn't ready and would delay needed standards. Everyone is watching the chipmakers for a breakthrough.
DTA has been understood for at least two decades but not previously extended to DSL. Below is a 1998 patent "Method of time-slot allocation in a TDMA communication system." It has been widely used in GPON and wireless.
Adtran's Paris demo was 106MHz based and demonstrated 750Mbps over 100 Meters of spooled coax. Ronan Kelly assures me the system will deliver the same bandwidth over a longer distance. He writes, "For practicality reasons, we only had a 100 meter spool with us for the event."
They sent me this note.
Please note that the demo solution had a less than ideal aggregate throughput of ~750 Mbps. We wanted to demonstrate the effect of DTA/DBA during demo not the overall performance of coax as a medium. We make note of the following demo speed limitations which all affected the overall speed performance compared to our current best estimation of the expected coax performance of future versions of the solution:
- ·Use of pre-standard DTA implementation within the demo system,
- ·Attenuation caused from the T-connector from the scope used in demo setup,
- ·Limited PON OLT traffic engineering and DBA optimization used as DPU uplink within the demo system
Results of Paris demo were as follows:
Splits in US and DS:
o Symmetric Case: Mds =18, Mus=17: DS 390Mbps, US 359Mbps
o DS preferred: Mds =28, Mus=7: DS 610Mbps, US 145Mbps
o US preferred: Mds = 13, Mus = 22: DS 277Mbps, US 467Mbps
The current best estimation of the expected coax DTA customer’s G.fast experience is a Total ETR of 880-900Mbps out to 200 meters or 600 feet RG-6 Coax. Note that on coax distances G.fast rate-reach beyond 200 meters (600 feet) does not matter as much, as the video signal does not reach beyond that distance.
The maximum expected TDD Ratio for DTA is from 30-5 to 5-30. This would result in the following performance with total ETR of 880-900Mbps:
DS = 900 x (30/35) = 771 Mbps
US = 880 x (30/35) = 754 Mbps
US 5748624 A
1. Field of the Invention
The present invention relates to a method of time-slot allocation in a time division multiple access (TDMA) communication system which allocates one or more time-slots in a TDMA frame for a communication signal to perform the communication, and, more particularly, to a method of efficient time-slot allocation for high transmission speed data communication.
2. Description of the Related Art
In conventional TDMA communication systems, there has been proposed a method in which a plurality of fixed number of time-slots are allocated to a communication signal having a higher transmission speed than the transmission speed of one time-slot in a TDMA frame.
An example of conventional methods of allocating a plurality of fixed number of time-slots in a TDMA frame is described in Japanese Patent Application Laid-Open No. Hei 2-203632.
FIGS. 1(A) and 1(B) show a system construction and a TDMA frame, respectively, for explaining this conventional technique.
This system is constituted by a public telephone network 10, a gateway exchange 20 for switching and connecting the public telephone network 10 and a mobile radio communication system which is adopting a TDMA communication system. The mobile radio communication system is constituted by a radio channel control station 35 connected to the gateway exchange 20, a base station 40 connected to the radio channel control station 35 and a plurality of mobile terminals 60 which can communicate, within a cell 50 where the base station 40 covers, with the base station 40 by radio signals.
The radio channel control station 35 has a function of allocating a plurality of fixed number of time-slots to a communication signal having a higher transmission speed than the transmission speed provided for one time-slot in a TDMA frame.
FIG. 1(B) is a diagram showing an example of the TDMA frame construction of the carrier when a plurality of time-slots are allocated to a communication signal having a higher transmission speed than the transmission speed provided for one time-slot in the TDMA frame. In this case, one time-slot is capable of transferring one channel of low transmission speed communication signal indicated by T1 or T2. In this time-slot provision, 4 time-slots are allocated to high transmission speed communication signal indicated by D1.
For an example, if one time-slot is provided for having a capability of transferring 32 kbps signal, communication signal of 64 kbps is allocated to two time-slots, and communication signal of 128 kbps is allocated to four time-slots.
In the aforementioned conventional time-slot allocating method, the TDMA frame is constructed such that one time-slot corresponds to the lowest transmission speed signal, and with respect to a higher transmission speed signal, various kinds of transmission speed signals are dealt with by allocating a plurality of fixed number of time-slots enough for transferring the data. Therefore, if a ratio of the number of higher transmission speed communication is larger than the lowest transmission speed communication in the TDMA communication system, the probability of requiring a plurality of idle time-slots to be allocated at the same time to a new communication request will be increased. As the result, there is the drawback that the probability of call loss is increased because the call request which needs a plurality of time-slots enough for transferring the data is rejected if sufficient idle time-slots are not available at the time of time-slots allocation.SUMMARY OF THE INVENTION
The objective of the present invention is to provide an efficient TDMA time-slot allocating method which is capable of flexible time-slots allocation for a high transmission speed communication for reducing the call loss of a newly requested call when a ratio of high transmission speed communication is relatively large in the communication system.
A method of time-slot allocation for a communication in a time division multiple access (TDMA) communication system which allocates one or more time-slots in a TDMA frame, comprises the following steps:
(1) detecting a request for new communication;
(2) examining whether number of idle time-slot required for the new communication detected is available;
(3) examining whether any of high transmission speed communication using a plurality of time-slots exist, if the number of idle time-slot required for the new communication is not available;
(4) releasing at least one time-slot from a plurality of time-slots being used for one of the high transmission speed communications existing; and
(5) allocating the released time-slot to the new communication requested.
According to the present invention, allocation of time-slots for the high transmission speed communication has a flexibility. Although all time-slots required for transmitting the data in the normal speed is preferable, it can be reduced depending on the availability of idle time-slot for a newly requested call. If there is not enough idle time-slot for the new call, a part of time-slots currently being used for the high transmission speed communication is released and used for the new call to avoid rejection of a call request due to non-availability of idle time-slot.
The method of time-slot allocation as set forth above further comprises the following steps in releasing at least one time-slot from a plurality of time-slots being used for one of the high transmission speed communications existing:
(1) examining the high transmission speed communication using a maximum number of time-slots;
(2) releasing at least one time-slot from a plurality of time-slots being used for the high transmission speed communication examined; and
(3) performing transmission speed adjustment depending on the number of time-slots being released.
The high transmission speed communication whose time-slot is partially released is selected from those which are using a maximum number of time-slots, and transmission speed adjustment should be performed because it is no longer being allocated a sufficient number of time-slots to support the current transmission speed.
When releasing time-slot of the high transmission speed communication, the following should also be considered:
(1) releasing at least one time-slot so that a number of time-slots of the high transmission speed communication being examined and a number of time-slots of the new high transmission speed communication become as equal as possible.
There is another aspect of the present invention.
A method of time-slot allocation for a communication in a TDMA communication system comprises the following steps:
(1) detecting any of idle time-slots becoming available due to completion of other communication;
(2) finding a high transmission speed communication using an insufficient number of time-slots; and
(3) allocating time-slots becoming available to the high transmission speed communication that is using the insufficient number of time-slots.
This is time-slot reallocation when idle time-slot becomes available. Those time-slots are to be reallocated to a high transmission speed communication having an insufficient number of time-slots.
The method of time-slot allocation as set forth (time-slot reallocation), further comprises the step of:
(1) changing over a high transmission speed communication from a different carrier, when the idle time-slots becoming available are no longer used in the same carrier but demand exists in a different carrier.
It means that idle time-slots becoming available are allowed to be allocated to a high transmission speed communication currently being allocated in the different carrier as far as this allocation contributes to efficient use of the communication system.