Claims:CLAIMS
We claim:

1. A system for establishing a device to device communication link in cellular networks using a TTG (transmit to receive transition gap) and a RTG (receive to transmit transition gap) of the cellular networks, the system comprising:
a base station (104) that is coupled to a cellular tower (102B);
one or more user equipments (108A-N) comprising a first user equipment (108A) and a second user equipment (108B), wherein the first user equipment (108A) is configured with a first user equipment cognitive engine (110A) and the second user equipment (108B) is configured with a second user equipment cognitive engine (110B);
a memory and a storage device; and
a processor in communication with the memory and the storage device, the communication processor executing machine readable program instructions for performing a method for establishing the device to device communication link in the cellular networks using the TTG (transmit to receive transition gap) and the RTG (receive to transmit transition gap), the method comprising:
performing a time synchronization through at least one of (i) a downlink reference signal from the base station (104), (ii) a GPS (Global Positioning System) timing signal, or (iii) a timing reference signal from a digital television (DTV);
scheduling a downlink bandwidth for the first user equipment (108A) at a starting of a downlink transmission interval, wherein the downlink transmission interval comprises radio frames, wherein the radio frames are divided into n sub frames of equal time interval based on a configuration of the cellular networks and the starting of the downlink transmission interval is a starting of a sub frame one; and
scheduling an uplink bandwidth for the first user equipment (108A) at an end of an uplink transmission interval to reduce a probability of overlapping signals at the TTG, wherein the one or more user equipments (108A-N) establishes the device to device communication link in a TTG timing interval or a RTG timing interval,
wherein the uplink transmission interval comprises radio frames, wherein the radio frames are divided into n sub frames of equal time interval based on a configuration of the cellular networks and the end of the uplink transmission interval is an end of a sub frame n.

2. The system for establishing the device to device communication link in cellular networks as claimed in claim 1, wherein the cellular networks comprises a time division duplex TDD, a frequency division duplex FDD, and a cellular digital packet data (CDPD).

3. The system for establishing the device to device communication link in cellular networks as claimed in claim 1, comprising a collaborative random access channel (CRACH) method to low latency networks for joining the one or more user equipments (108A-N) in a dense urban and cellular IoT networks using the device to device communication link, the collaborative random access channel (CRACH) method comprising:
scanning by the second user equipment (108B) for the first user equipment (108A) connected with the base station (104) when the base station (104) is not available for the second user equipment (108B);
establishing the device to device communication link between the first user equipment (108A) and the second user equipment (108B);
indicating a presence of second user equipment (108B) to the base station (104) by the first user equipment (108A) through a message;
allocating a bandwidth and announcing the bandwidth allocation in a downlink map from the base station (104) to the second user equipment (108B) through the device to device communication link established between the first user equipment (108A) and the second user equipment (108B); and
enabling the second user equipment (108B) to enter into the dense urban and the cellular IoT networks on the CRACH request through the first user equipment (108A) to the base station (104).

4. The system for establishing the device to device communication link in cellular networks as claimed in claim 3, wherein the method comprises sending an information on a second user equipment (108B) presence to the base station (104) by the first user equipment (108A).

5. The system for establishing the device to device communication link in cellular networks as claimed in claim 4, wherein the bandwidth allocation to the second user equipment (108B) is through a bypassing non-deterministic random access channel RACH process using a CRACH request.

6. The system for establishing the device to device communication link in cellular networks as claimed in claim 1, comprising a method for increasing a number of active users served by the base station (104) by establishing the device to device communication between the one or more user equipments (108A-N), the method comprising:
searching for the first user equipment (108A) presence which is connected to the base station (104);
establishing the device to device communication link with the first user equipment (108A) by the second user equipment (108B) on finding the first user equipment (108A) presence;
sending a request message to the first user equipment (108A) by the second user equipment (108B) to act as a relay node to connect to the base station (104); and
approving the second user equipment (108B) request, sent via the first user equipment (108A) for allowing the second user equipment (108B) to communicate with the base station (104) through the first user equipment (108A).

7. The system for establishing the device to device communication link in cellular networks as claimed in claim 6, wherein the method comprises scanning for the base station (104) downlink signal or synchronizing to a GPS signal or other timing reference signals when the second user equipment (108B) requests to join the dense urban and the cellular IoT networks.

8. A method for establishing a device to device communication link in cellular networks using a TTG (transmit to receive transition gap) and a RTG (receive to transmit transition gap), the method comprising:
a memory and a storage device; and
a processor in communication with the memory and the storage device, the communication processor executing machine readable program instructions for establishing the device to device communication link in the cellular networks using the TTG (transmit to receive transition gap) and the RTG (receive to transmit transition gap), the method comprising:
performing a time synchronization through at least one of (i) a downlink reference signal from a base station (104), (ii) a GPS (Global Positioning System) timing signal, or (iii) a timing reference signal from a digital television DTV;
scheduling a downlink bandwidth for a first user equipment (108A) at a starting of a downlink transmission interval and a second user equipment (108B) is outside of a coverage area from the base station (104),
wherein the coverage area is a geographical area in which the cellular networks offers a cellular service for the one or more user equipments (108A-N);
scheduling an uplink bandwidth for the first user equipment (108A) at an end of an uplink transmission interval to reduce overlapping signals at the TTG; and
establishing the device to device communication link in a TTG timing interval or a RTG timing interval by one or more user equipments (108A-N).

9. The method for establishing the device to device communication link in cellular networks as claimed in claim 8, comprising a collaborative random access channel (CRACH) method for low latency networks joining the one or more user equipments (108A-N) in a dense urban and cellular IoT networks using the device to device communication link, the collaborative random access channel method comprising:
scanning by the second user equipment (108B) for the first user equipment (108A) connected with the base station (104) when the base station (104) is not available for the second user equipment (108B);
establishing the device to device communication link between the first user equipment (108A) and the second user equipment (108B);
indicating a presence of second user equipment (108B) to the base station (104) by the first user equipment (108A) through a message;
allocating a bandwidth and announcing the bandwidth allocation in a downlink map from the base station (104) to the second user equipment (108B) through the device to device communication link established between the first user equipment (108A) and the second user equipment (108B); and
enabling the second user equipment (108B) to enter into the dense urban and the cellular IoT networks on the CRACH request through the first user equipment (108A) to the base station (104).

10. The method for establishing the device to device communication link in cellular networks as claimed in claim 8, comprising a method for extending the base station (104) coverage area without increasing a base station transmit power by establishing the device to device communication between the one or more user equipments (108A-N), the method comprising:
searching for the first user equipment (108A) presence which is connected to the base station (104) if the second user equipment (108B) fails to detect downlink signal from the base station (104);
establishing the device to device communication link with the first user equipment (108A) by the second user equipment (108B) on finding the first user equipment (108A) presence;
sending a request message to the first user equipment (108A) by the second user equipment (108B) to act as a relay node to connect to the base station (104); and
approving the second user equipment (108B) request, sent via the first user equipment (108A) for allowing the second user equipment (108B) to communicate with the base station (104) through the first user equipment (108A).

Dated this 24th day of April, 2019
Signature of Patent Agent:

Bala Arjun Karthik
(IN/PA 1021)

, Description:SYSTEM AND METHOD FOR ESTABLISHING A DEVICE TO DEVICE COMMUNICATION LINK IN CELLULAR NETWORKS

BACKGROUND
Technical Field
[0001] The embodiments herein generally relate to cellular networks, and more particularly, to a system and method for establishing a device to device communication link in cellular networks.
Description of the Related Art
[0002] Currently in cellular network deployment, a base station is configured once during deployment and most parameters related to random-access channel (RACH) are fixed during such configuration. Such fixed parameters might not be suitable for highly dense cellular networks resulting in RACH back offs which leads to huge cellular network entry delays. Delays in entering the cellular network are not acceptable in critical services.
[0003] Accordingly, there remains a need for a system and method for establishing a device to device communication link in cellular networks to enable faster network entry.
SUMMARY
[0004] This summary is provided to introduce a selection of concepts in a simplified form that is further described below in the Detailed Description. This Summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.
[0005] In an aspect, a system for establishing a device to device communication link in cellular networks using a TTG (transmit to receive transition gap) and a RTG (receive to transmit transition gap) of the cellular networks is disclosed. The system includes a base station, one or more user equipments, a memory and a storage device, and a processor. The base station is coupled to a cellular tower. The one or more user equipments includes a first user equipment and a second user equipment. The first user equipment is configured with a first user equipment cognitive engine and the second user equipment is configured with a second user equipment cognitive engine. In an embodiment, the processor in communication with the memory and the storage device, the processor executing machine readable program instructions for performing a method for establishing the device to device communication link in the cellular networks using the TTG (transmit to receive transition gap) and the RTG (receive to transmit transition gap). The method includes performing a time synchronization through at least one of (i) a downlink reference signal from the base station, (ii) a GPS (Global Positioning System) timing signal, or (iii) a timing reference signal from a digital television DTV, scheduling a downlink bandwidth for the first user equipment at the starting of a downlink transmission interval. The downlink transmission interval includes radio frames. The radio frames are divided into n sub frames of equal time interval based on a configuration of the cellular networks. The starting of the downlink transmission interval is a starting of a sub frame one and scheduling an uplink bandwidth for the first user equipment at an end of an uplink transmission interval to reduce the probability of overlapping signals at the TTG. The uplink transmission interval includes radio frames. The radio frames are divided into n sub frames of equal time interval based on a configuration of the cellular networks. The end of the uplink transmission interval is an end of a sub frame n. The one or more user equipments establishes the device to device communication link in a TTG timing interval or a RTG timing interval.
[0006] In another aspect, a method for establishing a device to device communication link in cellular networks is disclosed. The method includes performing a time synchronization through at least one of (i) a downlink reference signal from the base station (104), (ii) a GPS (Global Positioning System) timing signal, or (iii) a timing reference signal from a digital television DTV, scheduling a downlink bandwidth for the first user equipment at a starting of a downlink transmission interval. A second user equipment is outside of a coverage area from the base station and the coverage area is a geographical area in which the cellular networks offers a cellular service for the one or more user equipments, and scheduling an uplink bandwidth for the first user equipment later in a uplink transmission interval to reduce overlapping signals at the TTG. The one or more user equipments establishes the device to device communication link in a TTG timing interval or a RTG timing interval.
[0007] 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 THE DRAWINGS
[0008] The embodiments herein will be better understood from the following detailed description with reference to the drawings, in which:
[0009] FIG. 1 illustrates a system view of a cellular deployment including a base station according to some embodiments herein;
[0010] FIG. 2 illustrates the base station with a Random-Access Channel (RACH) according to some embodiments herein;
[0011] FIG. 3 illustrates a User Equipment (UE) cognitive engine with the random-access channel according to some embodiments herein;
[0012] FIG. 4 illustrates a collaborative random-access channel (RACH) process for one or more user equipments UEs according to some embodiments herein;
[0013] FIG. 5 illustrates a collaborative random-access channel (RACH) process according to some embodiments herein;
[0014] FIG. 6A illustrates a device to device bandwidth allocation without using the collaborative random-access channel RACH according to some embodiments herein;
[0015] FIG. 6B illustrates a device to device bandwidth allocation using the collaborative random-access channel RACH according to some embodiments herein;
[0016] FIGS. 7A-7B illustrate a method for establishing the device to device communication link between the user equipment UE and a base station scheduler according to some embodiments herein;
[0017] FIGS. 8A-8B illustrate a method for CRACH according to some embodiments herein;
[0018] FIG. 9 illustrates a method for extending the base station coverage area without increasing a base station transmit power according to some embodiments herein; and
[0019] FIGS. 10 illustrates a method for establishing a device to device communication link in a cellular network using TTG (Transmit to receive transition gap) and RTG (receive to transmit transition gap) according to some embodiments herein.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0020] 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.
[0021] As mentioned, there remains a system and method for establishing a device to device communication link in cellular networks. The embodiments herein achieve this by configuring a cognitive engine on a User Equipment (UE) which gathers data from multiple sources for achieving an optimized power, an enhanced range random-access channel (RACH). Referring now to the drawings, and more particularly to FIGS. 1 through 10, where similar reference characters denote corresponding features consistently throughout the figures, there are shown preferred embodiments.
[0022] FIG. 1 is a block diagram 100 of a system of a cellular deployment including a base station 104 according to some embodiments herein. The block diagram 100 includes at least two cellular towers 102A-102B, the base station 104 at the cellular tower 102A, an evolved packet core 106, one or more user equipments 108A-N and one or more first user cognitive engines 110A-N. The evolved packet core (EPC) 106 is a framework for providing converged voice and data on the cellular networks. The one or more user equipments 108A-N includes a first user equipment 108A, a second user equipment 108B, and an nth user equipment 108N, the first user equipment 108A is configured with a first User Equipment (UE) cognitive engine 110A. The second user equipment 108B is configured with a second User Equipment (UE) cognitive engine 110B. The nth user equipment 108N is configured with an nth user equipment (UE) cognitive engine 110N. The base station 104 and the one or more first user equipments UEs cognitive engines 110A-N include a Random-Access Channel (RACH). In some embodiments, the RACH at the first user equipment 108A provides faster entry to cellular networks which reduces consumption of a Radio Frequency (RF) power at the cellular tower 102B.
[0023] FIG. 2 is a block diagram 200 of the base station 104 with a Random-Access Channel (RACH) according to some embodiments herein. The base station 104 includes one or more inputs and one or more outputs. The one or more inputs are (i) a Global Positioning System (GPS) sync clock 202, (ii) a geographic (GEO) location 204, (iii) a terrain and propagation model 206, and (iv) a schedule information 208. The GPS sync clock 202 provides geolocation and time information of the first user equipment 108A to a GPS receiver that is anywhere on earth or near the earth where there is an unobstructed line of sight to one or more GPS satellites. The GEO location 204 is a process of finding, determining and providing an exact location of the first user equipment 108A. The GEO location 204 enables a location of the first user equipment 108A based on geographical coordinates and measurements.
[0024] The terrain and propagation model 206 is a characterization of radio wave propagation as a function of frequency, distance and other conditions. The terrain and propagation model 206 predict path loss along with a communication link. The schedule information 208 for the base station 104 of the cellular tower 102B provides information on how the base station 104 allocates a downlink and an uplink to the one or more user equipments 108A-N.
[0025] The base station 104 provides proper convergence of the cellular networks based on advice or an estimation on the timing advancement announcement 212. The collaborative RACH allocation 214 indicates the base station 104 in the cellular tower 102B includes edge nodes. The edge nodes provide information on all the user equipment in cellular network. In some embodiments, the edge nodes act as a relay node. The relay node extends a coverage area of the cellular network. The base station 104 marks the edge nodes as the relay node. The second user equipment 108B enters into the cellular network instead of directly entering to the base station 104, if the second user equipment 108B comes near to the first user equipment 108A. The base station 104 sends the probability of success 216 for the RACH, if the second user equipment 108B enters into the cellular network then the probability of success 216 of the second user equipment 108B attaching to the base station 104 is calculated. In some embodiments, cellular networks include uplink and a downlink. The uplink and the downlink are divided into resource slots.
[0026] For example, consider a defined schedule (at 10 am daily) of data transmission from the second user equipment 108B to the base station 104. The second user equipment 108B expects a downlink command from the base station 104. The downlink command includes resource information. The resource information includes one or more information on a network load indicator, the schedule information 208 and a distribution of the one or more user equipments 108A-N and how resources are allocated and encapsulated in a downlink map. For example, the downlink map includes an information on the one or more user equipments 108A-N such as the first user equipment 108A is allocated with 1 Megabits per second (Mbps) and the second user equipment 108B is allocated with 2 Mbps. The downlink map further includes the resource information which includes a number of resource slots in the second user equipment 108B and properties of the resource slots such as a MCS value coding, a modulation and code rate values such as a Quadrature Phase Shift Keying QPSK, a 64 quadrature amplitude modulation QAM or a 1/2 code rate. In some embodiments, the one or more user equipments 108A-N includes the first user equipment 108A, the second user equipment 108B, a third user equipment 108C, a fourth user equipment 108D, and an Nth user equipment 108N.
[0027] FIG. 3 is a block diagram 300 the first user equipment cognitive engine 110A with a random-access channel RACH according to some embodiments herein. The first user equipment cognitive engine 110A includes one or more inputs and one or more outputs. The one or more inputs includes at least one of (i) a global position system GPS sync clock 302, (ii) a periodic pre-configured schedule 304, (iii) a user equipment category classification 306, (iv) a connection probability index 308, (v) a back off indicator 310, (vi) network load indicator 312, and (vii) a schedule information 314. The GPS sync clock 302 provides geolocation and time information of the user equipment UE 108A to a GPS receiver anywhere on or near the Earth where there is an unobstructed line of sight to four or more GPS satellites. The schedule information 314 provides information on how the base station 104 allocates a downlink and an uplink to the one or more user equipments 108A-N.
[0028] The one or more output includes at least one of (i) a collaborative RACH request 316, (ii) a neighboring discovery and profiling 318, and (iii) a base station profiling 320. The collaborative RACH request 316 requests the base station 104 to connect to the cellular network. The neighboring discovery and profiling 318 detect if there is the first user equipment 108A present in the cellular network which behaves as an edge node for connecting the second user equipment 108B to the base station 104. In some embodiments, the first user equipment 108A is a neighboring user equipment and the second user equipment is a new user equipment.
[0029] FIG. 4 is a block diagram 400 of a collaborative random-access channel RACH process for one or more user equipments 108A-N according to some embodiments herein. The collaborative random-access channel RACH process includes the first cellular tower 102A, the second cellular tower 102B, the first user equipment cognitive engine 110A, the evolved packet core EPC 106, the base station 104, and the one or more user equipment 108A-N.
[0030] FIG. 5 is a block diagram 500 a collaborative random-access channel RACH process according to some embodiments herein. The collaborative random-access channel RACH process includes the second user equipment 108B, the first user equipment 108A, the cellular tower 102B, and a cellular network coverage area 502. The base station 104 allocates resource slots at a cellular deployment of a device to device communication. A device to device communication bandwidth is optimally allocated such that it overlaps a Transmit Transition Gap (TTG) and a Receive Transition Gap (RTG). A schedule information 314 from the first user equipment cognitive engine 110A allocates a downlink and an uplink of the first user equipment’s 108A based on at least one of a device to device communication link is configured across entire network deployment, the second user equipment 108B synchronizes to the GPS sync clock 302 and a timing advancement signals, e.g. digital television DTV sync. The second user equipment 108B searches for a base station downlink synchronization signal. The second user equipment 108B searches for a first user equipment 108A uplink signals on detection of the first user equipment 108A if the base station downlink synchronization signal is not detected by the second user equipment 108B. The second user equipment 108B sends a collaborative RACH request to the first user equipment 108A using a device to device communication slot. The first user equipment 108A decides to act as an edge node based on a downlink map. The collaborative RACH selects the first user equipment 108A (the user equipment UE cognitive engine 110A) based on the base station 104 announcements in the downlink map and a probability of success index. The first user equipment 108A establishes the device to device (D2D) link with the second user equipment 108B. In an embodiment, the first user equipment 108A act as a forwarding node. The first user equipment 108A indicates the base station 104 about a second user equipment 108B presence.
[0031] In some embodiments, the second user equipment 108B is inside the coverage area of the cellular network. The second user equipment 108B may establish the device to device communication with the first user equipment 108A. In some embodiments, the collaborative random-access channel RACH process detects the users at an edge. The edge is D2 that is a distance. For example, in the collaborative RACH after detecting the second user equipment 108B, the base station 104 provides a command to the first user equipment 108A to act as an extender if the second user equipment (108B) is not connected to the base station (104) or a bandwidth is not allocated to the second user equipment (108B) by the base station (104). In an embodiment, the second user equipment (108B) is not connected to the base station (104) due to network congestion. The bandwidth is not allocated to the second user equipment (108B) by the base station (104) due to network congestion. In another embodiment, the second user equipment (108B) is not connected to the base station (104) due to network coverage (for example the second user equipment (108B) is outside of the cellular network). The second user equipment 108B detects the first user equipment 108A and the second user equipment 108B provides a command to the first user equipment 108A to act as a relay node so that the user joins the cellular network.
[0032] The probability of attachment if the cellular network is fully loaded then the second user equipment 108B might get attached to the first user equipment 108A so that the probability of success (the base station includes an information on how the one or more user equipments trying to access the cellular network) index is calculated by the collaborative RACH. If the probability of success is high then the second user equipment 108B gets attached to the cellular network and if the probability of success is low then second user equipment 108B won’t get attached to the cellular network. The information on the probability of success is in the downlink map. In an embodiment, if the probability of success is low then first user equipment 108A will act as a relay instead of directly attaching to the cellular network through the base station 104.
[0033] FIG. 6A illustrates a device to device bandwidth allocation without using the collaborative random-access channel RACH according to some embodiments herein. Typically, there is a gap between the uplink and the downlink. The first user equipment 108A receives the data, then the first user equipment 108A responds directly when the first user equipment 108A sends a data in a downlink path. The Transmit Transition Gap (TTG) 606 and the Receive Transition Gap (RTG) 608 are determined during the time of the deployment of the cellular network based on an area the cellular network has to cover.
[0034] FIG. 6B illustrates a device to device bandwidth allocation using the collaborative random-access channel RACH according to some embodiments herein. If a hole in transmission time is a significant amount of time the TTG 606 and the RTG 608 may be used for the D2D communication link. For the D2D communication between the first user equipment 108A can be provided by the TTG and RTG. The first user equipment 108A is synchronized with a GPS DTV synchronization signal and the base station 104 also synchronize with the GPS if the second user equipment 108B comes inside the cellular network, then.
[0035] The second user equipment 108B searches for available downlink signal, if the downlink signal is not detected and if the second user equipment 108B is out of the coverage area then the second user equipment 108B searches for the first user equipment 108A if yes then the second user equipment 108B sends collaborative RACH request to first user equipment 108A through uplink. The collaborative RACH request is sent through TTG 606 and RTG 608 once the request reaches the first user equipment 108A then the first user equipment 108A attaches the second user equipment 108B to the base station 104 else the first user equipment 108A informs base station 104 to increase power so that the second user equipment 108B comes inside the coverage area of the cellular network. If the first user equipment 108A is not inside the coverage area then the second user equipment 108B sees no cellular network. For example, in a Long-Term Evolution LTE technology, there is a hole in time and during the hole, there is no transmission of a data but still, without involving the base station the first user equipment 108A and the second user equipment 108B can communicate with each other using the D2D.
[0036] FIGS. 7A-7B illustrate a method for establishing the device to device communication link between the user equipment UE and a base station scheduler according to some embodiments herein. At step 704, the method 700 includes the second user equipment 108A starts the method 700 of establishing the device to device communication link with the first user equipment 108A. At step 706, the second user equipment 108B establishes a timing synchronization using the base station downlink, the GPS, the timing reference signal such as DTV 708. At step 710, the second user equipment 108B searches for the first user equipment 108A. At step 712, the second user equipment UE 108B establishes the device to device communication link using TTG and RTG with the first user equipment 108A. At step 716, the base station scheduler 702 finds a distance of a user equipment from the base station 104. At step 718, the base station scheduler 702 allocates downlink to the far user equipment at the beginning of the downlink transmission interval. The downlink transmission interval includes radio frames and the radio frames are divided into n sub frames of equal time interval based on a configuration of the cellular networks. The starting of the downlink transmission interval is a starting of a sub frame one. At step 720, the base station scheduler 702 allocates uplink to the far user equipment at the end of the uplink transmission interval. The uplink transmission interval includes radio frames. The radio frames are divided into n sub frames of equal time interval based on a configuration of the cellular networks. The end of the uplink transmission interval is an end of a sub frame n.
[0037] FIGS. 8A-8B illustrate a method for CRACH according to some embodiments herein. At step 802, the method 800 for CRACH started by the second user equipment 108B. At step 804, a timing synchronization is established using the base station downlink, the GPS, the timing reference signal such as DTV 806 by the second user equipment 108B. At step 808, the second user equipment 108B searches for the first user equipment 108A. At step 810, the device to device communication link using TTG and RTG for the first user equipment 108A is established by the second user equipment 108B. At step 812, a CRACH request is sent to the base station 104 via the first user equipment 108A by the second user equipment 108B. At step 814, the method 800 for CRACH is started by the base station scheduler 1002. At step 816, a bandwidth is allocated to the second user equipment 108B by the base station scheduler 702 on reception of a CRACH message.
[0038] FIG. 9 is a flow diagram that illustrates a method 900 for extending base station coverage area without increasing base station transmit power according to some embodiments herein. At step 902, the method 900 for extending the base station coverage area without increasing the base station transmit power is started by the second user equipment 108B. At step 904, a timing synchronization is established using the base station downlink, the GPS, the timing reference signal such as DTV 906. At step 908, the first user equipment 108A is searched by the second user equipment 108B. At step 910, the device to device communication link using TTG and RTG for the first user equipment 108A is established by the second user equipment 108B. At step 912, the first user equipment 108A acts as a relay node to connect the second user equipment 108B to the base station 104.
[0039] FIG. 10 is a flow diagram illustrating a method 1000 for establishing a device to device communication link in a cellular network using TTG (Transmit to receive transition gap) and RTG (receive to transmit transition gap) according to some embodiments herein. At step 1002, a time synchronization is performed through at least one of (i) a downlink reference signal from a base station (104), (ii) a GPS (Global Positioning System) timing signal, or (iii) a timing reference signal from a digital television DTV. At step 1004, a downlink bandwidth is scheduled for a first user equipment (108A) at a starting of a downlink transmission interval. A second user equipment (108B) is outside of a coverage area from the base station (104). The coverage area is a geographical area in which the cellular networks offers a cellular service for the one or more user equipments (108A-N). At step 1006, an uplink bandwidth is scheduled for the first user equipment (108A) at an end of an uplink transmission interval to reduce overlapping signals at the TTG. At step 1008, the device to device communication link is established in a TTG timing interval or a RTG timing interval by one or more user equipments (108A-N).
[0040] 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 appended claims.