FORM 2
The Patent Act 1970
(39 of 1970)
&
The Patent Rules, 2005

COMPLETE SPECIFICATION
(SEE SECTION 10 AND RULE 13)

TITLE OF THE INVENTION

“Predictive Latency Based Compression of Data for bi-directional IP traffic over satellite links”
APPLICANTS:

Name Nationality Address
Devas Multimedia Private Limited
Indian Prema Gardenia, 357/6, 1st Cross, I Block, Jayanagar, Bangalore-11

The following specification particularly describes and ascertains the nature of this invention and the manner in which it is to be performed:-

FIELD OF INVENTION
[001] This invention relates to satellite based communication networks, and more particularly to techniques for improving performance using latency inherent in satellite based communication networks.

BACKGROUND OF INVENTION
[002] Very long distances are involved in Satellite communication links, normally in the order of thousands of kilometers. Such long distances result in latency being introduced into satellite communication networks. Latency is the time taken for data communication between a message being sent by a module in the satellite communication network and a response to the message being received by the module. The latency in satellite communication networks are of a much higher order as compared to other communication networks such as wired and terrestrial-wireless networks.
[003] In current systems, the transmitters present in the satellite communication network transmit do take the latency into account while deciding certain parameters of the TCP-IP protocol such as “Sliding Window”. However there are no systems and methods which take advantage of latency and compress data based on latency conditions.

OBJECT OF INVENTION
[004] The principal object of this invention is to techniques for improving performance using latency inherent in satellite based communication networks.

STATEMENT OF INVENTION
[005] Accordingly the invention provides a method and system for transmitting data in a satellite communication network, the method comprising of a transceiver estimating delay time on a communication link in the network, wherein the communication link is a bidirectional communicational link used by the transceiver; the transceiver estimating waiting time for data to be transmitted; and the transceiver selecting a compression algorithm for compressing the data, based on a comparison between the waiting time and a pre-specified time period.
[006] These and other aspects of the embodiments herein will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood, however, that the following descriptions, while indicating preferred embodiments and numerous specific details thereof, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the embodiments herein without departing from the spirit thereof, and the embodiments herein include all such modifications.

BRIEF DESCRIPTION OF FIGURES
[007] This invention is illustrated in the accompanying drawings, throughout which like reference letters indicate corresponding parts in the various figures. The embodiments herein will be better understood from the following description with reference to the drawings, in which:
[008] FIG. 1 depicts a satellite communication network, according to embodiments as disclosed herein;
[009] FIG. 2 depicts a transceiver in a satellite communication network, according to embodiments as disclosed herein; and
[0010] FIG. 3 is a flowchart depicting a process, according to embodiments as disclosed herein.

DETAILED DESCRIPTION OF INVENTION
[0011] The embodiments herein and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments that are illustrated in the accompanying drawings and detailed in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.
[0012] The embodiments herein achieve better optimizations on data transfer by utilizing latency present in satellite communication networks. Referring now to the drawings, and more particularly to FIGS. 1 through 3, where similar reference characters denote corresponding features consistently throughout the figures, there are shown preferred embodiments.
[0013] Fig. 1 depicts a satellite communication system, according to embodiments as disclosed herein. The satellite communication system comprises of an earth station 102, a satellite 103 and a user terminal 104. The links between the earth station 102, satellite 103 and the user terminal 104 are bi-directional satellite links which have known amounts of delay across each satellite link. The earth station 102, satellite 103 and the user terminal 104 comprise of a transceiver module 101. The transceiver module 101 sends packets in bursts over the communication link and receives responses from the module at the other end of the communication link. The transceiver 101 estimates the delay based on the difference between the time the packets were sent and the time the response was received. The estimated delay is influenced by latency delay associated with the satellite link plus delays caused due to queuing up of acknowledgements and responses in the network. The transceiver 101 analyzes the raw data which is to be transmitted across the communication link. Based on the analysis of the raw data and the estimated delay, the transceiver 101 estimates the waiting time which the data has to wait before the data can be transmitted across the link. Based on the waiting time, the transceiver 101selects an appropriate compression technique for compressing the data. If the transceiver 101 estimates that the waiting time is greater than a specified time, then the transceiver 101 selects a compression algorithm which achieves higher compression rates, for example, a PAQ algorithm. If the transceiver 101 estimates that the waiting time is less than a specified time, then the transceiver 101 selects a compression algorithm which achieves faster compression rates, for example, a LZO (Lempel-Ziv-Oberhumer) algorithm. The transceiver 101 compresses the data with the selected compression technique and transmits the compressed data using the satellite communication link. The transceiver 101 may also send the data without compression, if the waiting time is less than the time taken by the fastest compression algorithm to compress the data.
[0014] FIG. 2 depicts a transceiver in a satellite communication network, according to embodiments as disclosed herein. The transceiver 101 comprises of a prediction engine 201, a controller 202, a compression module, a memory 204, a transmitter 205 and a receiver 206. The transmitter 205 sends packets in bursts over the communication link and the receiver 206 receives responses from the module at the other end of the communication link. The controller 202 is aware of the time the packets were sent by the transmitter 205 and the time the response was received by the receiver 206 and informs the times to the prediction engine 201. The prediction engine 201estimates the delay based on the difference between the time the packets were sent and the time the response was received and informs the delay time to the controller 202. The controller 202 analyzes the raw data which is to be transmitted across the communication link. Based on the analysis of the raw data and the estimated delay, the controller 202 estimates the waiting time which the data has to wait in the memory 204 before the data can be transmitted across the link. The controller 202 informs the waiting time to the compression module 203. Based on the waiting time, the compression module 203 selects an appropriate compression technique for compressing the data. If the compression module 203 estimates that the waiting time is greater than a specified time, then the compression module 203 selects a compression algorithm which achieves higher compression rates, for example, a PAQ algorithm. If the compression module 203 estimates that the waiting time is less than a specified time, then the compression module 203 selects a compression algorithm which achieves faster compression rates, for example, a LZO (Lempel-Ziv-Oberhumer) algorithm. The compression module 203 compresses the data with the selected compression technique and the transmitter 205 transmits the compressed data using the satellite communication link. If the compression module 203 detects that the waiting time is less than the time taken by the fastest compression algorithm to compress the data, the compression module 203 does not compress the data and the transmitter 205 transmits the data without compression.
[0015] FIG. 3 depicts a flowchart, according to embodiments as disclosed herein. The transceiver 101 estimates (301) the delay based on the difference between the time the packets were sent in bursts over the communication link and the time the response was received from the module at the other end of the communication link. The transceiver 101 analyzes (302) the raw data which is to be transmitted across the communication link. Based on the analysis of the raw data and the estimated delay, the transceiver 101 estimates (303) the waiting time which the data has to wait before the data can be transmitted across the link. The transceiver 101 checks (304) if the waiting time is less than the time taken by the fastest compression algorithm to compress the data. If the waiting time is greater than the time taken by the fastest compression algorithm to compress the data, the transceiver 101selects (305) an appropriate compression technique for compressing the data based on the waiting time. The transceiver 101 compresses (306) the data with the selected compression technique and transmits (307) the compressed data using the satellite communication link. If there is no sufficient time for compressing the data, the transceiver 101 sends (307) the data without compression. The various actions in method 300 may be performed in the order presented, in a different order or simultaneously. Further, in some embodiments, some actions listed in FIG. 3 may be omitted.
[0016] Consider the illustration given below, where the shaded blocks (N, N+1) are the blocks being transmitted currently. Each of the blocks is a 64KB chunk of data and the data is being transmitted over a 1Mbps satellite link. The time to send one block is approximately 52 seconds ((64 x 1024 x 8)/ (1000000)). Consider that the typical satellite link latency is approximately 1.2 seconds. The waiting time is computed as 1.72 seconds approximately (1.2 + 0.52)
N N+1 N+2 N+3 N+4 N+5

[0017] Here, the transceiver may group the blocks next in queue (N+2, N+3, …….).The transceiver 101 may group the blocks N+2 and N+3 together and the blocks N+4 and N+5 together as depicted below.
N N+1 N+2 N+3 N+4 N+5

[0018] The transceiver 101 checks if the waiting time of the combined block is greater than the time required to compress the blocks. If the waiting time of the combined block is greater than the time required to compress the blocks, then the blocks are compressed using a suitable algorithm based on the waiting time, as depicted below.
N N+1 (N+2) + (N+3) (N+4) +
(N+5)

[0019] The example above depicts a scenario where 50% compression is achieved for the waiting blocks, hereby increasing the throughput also by 50%.
[0020] The above example depicts combining two blocks; however it is obvious to a person of ordinary skill in the art that the transceiver may combine any number of blocks to achieve the desired compression.
[0021] Embodiments disclosed herein may be implemented at the application level. The application layer estimates latency of the link and compresses data before handing off the data to the TCP/IP stack for transmitting. The application layer is also responsible for decompressing after receiving data from the TCP/IP stack.
[0022] Embodiments disclosed herein may be implemented on the TCP/IP stack. Packet level compression is implemented alongside TCP/IP window buffering (based on RTT). Options field of TCP/IP protocol need to be used to flag compressed packets. TCP/IP stack at the receiver also needs to be aware and responsible for decompressing
[0023] Embodiments disclosed herein achieve better optimizations on data transfer in satellite communications by using techniques that can make use of delays in the satellite communication network to perform better. Depending on the content of the message (repetitiveness of data) and the length of the messages, embodiments herein result in better utilization of link time as well as faster delivery of messages. Embodiments herein require changing the payload of the IP packet only and no changes are required to be made to the IP layer or any other layers of the TCP-IP stack.
[0024] Embodiments herein require changing either the application layer above the TCP/IP stack or the TCP/IP stack itself or both. If the changes are implemented within the TCP/IP stack (i.e. the changes are made to packets within the TCP/IP stack), then the options field of the TCP/IP protocol need to be used to flag to the receiving TCP/IP stack that packets have been compressed. Additionally, the TCP/IP stack at the receiver would also need to be modified in order to understand the same.
[0025] The embodiments disclosed herein can be implemented through at least one software program running on at least one hardware device and performing network management functions to control the network elements. The network elements shown in Fig. 1 and 2 include blocks which can be at least one of a hardware device, or a combination of hardware device and software module.
[0026] The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.

WE CLAIMS:-
1. A method for transmitting data in a satellite communication network, said method comprising of
A transceiver estimating delay time on a communication link in said network, wherein said communication link is a bidirectional communicational link used by said transceiver;
Said transceiver estimating waiting time for data to be transmitted; and
Said transceiver selecting a compression algorithm for compressing said data, based on a comparison between said waiting time and a pre-specified time period.
2. The method, as claimed in claim 1, wherein said method further comprises of said transceiver estimating said delay time based on difference between time a previous data was transmitted and time a response to said previous data was received.
3. The method, as claimed in claim 1, wherein method further comprises of said transceiver estimating said waiting time using analysis of said data and said delay time
4. The method, as claimed in claim 1, wherein said method further comprises of said transceiver selecting said compression algorithm
5. The method, as claimed in claim 1, wherein said method further comprises of
Said transceiver compressing said data using said compression algorithm; and
Said transceiver transmitting said data.
6. The method, as claimed in claim 1, wherein said method further comprising of
Said transceiver selecting said compression algorithm only if there is sufficient time to compress said data using said compression algorithm.
7. A system performing a method as in at least one of preceding method claims 1 to 6.

Dated June 3, 2011

Dr. Kalyan Chakravarthy
Patent Agent

ABSTRACT
Predictive latency based compression of data for satellite based bi-directional IP traffic. This invention relates to satellite based communication networks, and more particularly to techniques for improving performance using latency inherent in satellite based communication networks. The embodiments herein achieve better optimizations on data transfer by utilizing latency present in satellite communication networks by using techniques that can make use of delays in the satellite communication network to perform better. Depending on the content of the message (repetitiveness of data) and the length of the messages, embodiments herein result in better utilization of link time as well as faster delivery of messages. FIG. 1