CLIAMS:We claim:
1. A TDMA based device (1000), the device (1000) comprising:
a processor (1001) to process a dynamic TDMA signal; and
a transceiver (1003) to transmit and/or receive the dynamic TDMA signal, wherein each frame of the dynamic TDMA signal comprises a plurality of data slots and a plurality of control slots, wherein the plurality of control slots comprises at least one Network Control Slot (NCS), and wherein the at least one NCS comprises: (i) an inlet guard slot, (ii) a PHY-preamble slot, (iii) a MAC header slot, (iv) a slot for carrying MAC control information (MCI), (v) a slot for carrying a payload for higher layer control (vi) an outlet guard slot.
2. The device (1000) as claimed in claim 1, wherein the slot for carrying the payload for higher layer control comprises one or more of a slot for carrying time critical tactical messages, a slot for carrying routing control packets, and a slot for application signalling messages.
3. The device (1000) as claimed in claim 1, wherein the slot for carrying time critical tactical messages, the slot for carrying routing control packets, and the slot for application signalling messages are utilized according a predefined priority.
4. The device (1000) as claimed in claim 1, wherein the at least one NCS comprises a 270 µs slot for the inlet guard slot, a 1547 µs slot for carrying control information, and a 183 µs slot for the outlet guard slot.
5. The device (1000) as claimed in claim 1, wherein the PHY preamble has size of 128 bits, the MAC header has size of 80 bits, and the MCI has size of 320 bits.
6. The device (1000) as claimed in claim 1, wherein the slot for carrying a payload for higher layer control has a combined size of 1921 bits.
7. The device (1000) as claimed in claim 1, wherein the MAC header, the MCI, the time critical tactical messages, the routing control packets, and the application signalling messages are Forward Error Correction (FEC) encoded.
8. The device (1000) as claimed in claim 1, wherein the plurality of control slots further comprises a Network Entry Slot (NES).
9. The device (1000) as claimed in claim 8, wherein the NES comprises a 270 µs slot for a first guard time distribution, a 1547 µs slot for carrying control information, and a 183 µs slot for a second guard time distribution.
10. The device (1000) as claimed in claim 9, wherein the control information comprises a PHY preamble, a MAC header, and MCI.
11. The device (1000) as claimed in claim 10, wherein the PHY preamble has a size of 128 bits, the MAC header has a size of 80 bits, and the MCI has a size of 320 bits.
12. The device (1000) as claimed in claim 10, wherein the MAC header and the MCI are FEC encoded.
13. The device (1000) as claimed in claim 1, wherein each of the plurality of data slots comprises a 270 µs slot for a first guard time distribution, a 1547 µs slot for carrying payload data, and a 183 µs slot for a second guard time distribution.
14. The device (1000) as claimed in claim 13, wherein the payload data comprises a PHY preamble, a MAC header, and traffic data.
15. The device (1000) as claimed in claim 14, wherein the PHY preamble has size of 128 bits, the MAC header has size of 80 bits, and the traffic data has size of 2241 bits.
16. The device (1000) as claimed in claim 14, wherein the MAC header and the traffic data are FEC encoded.
17. The device (1000) as claimed in claim 1, wherein the plurality of control slots comprises a Network Entry Slot (NES) and 16 Network Control Slot (NCS), and wherein the plurality of data slots comprises 28 data slots.
18. The device (1000) as claimed in claim 1, wherein duration of each of the plurality of data slots and each of the plurality of control slots is 2 ms.
19. The device (1000) as claimed in claim 1, wherein total duration of the each frame is 90 ms.
20. The device (1000) as claimed in claim 1, wherein the device (1000) meets one or more requirements of - an update rate less than 10 Hz, number of nodes equal to 16, a codec type of Mixed-Excitation Linear Predictive enhanced (MELPe), voice latency less than 120 ms, a radio range about 40 Km, frequency hopping rate of 500 hops, and throughput about 1Mbps.
21. The device (1000) as claimed in claim 1, the dynamic TDMA signal meets the requirements of UHF 1Mbps MANET waveform.
22. The device (1000) as claimed in claim 1, further comprising:
a memory (1002) to store the dynamic TDMA signal; and
an antenna (1004) to convert the dynamic TDMA signal into a radio signal and vice versa.
23. The device (1000) as claimed in claim 1, wherein the device (1000) is capable of communicating with a 1-Mbps self-forming radio network (1100).
24. A TDMA frame structure, comprising:
a plurality of data slots; and
a plurality of control slots having at least one Network Control Slot (NCS), wherein the at least one NCS comprises: (i) an inlet guard slot, (ii) a PHY-preamble slot, (iii) a MAC header slot, (iv) a slot for carrying MAC control information (MCI), (v) a slot for carrying a payload for higher layer control, and (vi) an outlet guard slot.
25. The TDMA frame structure as claimed in claim 24, wherein the slot for carrying the payload for higher layer control comprises one or more of a slot for carrying time critical tactical messages, a slot for carrying routing control packets, and a slot for application signalling messages.
26. The TDMA frame structure as claimed in claim 25, wherein the slot for carrying time critical tactical messages, the slot for carrying routing control packets, and the slot for application signalling messages are utilized according a predefined priority.
27. The TDMA frame structure as claimed in claim 24, wherein the plurality of control slots further comprises a Network Entry Slot (NES).
28. The TDMA frame structure as claimed in claim 24, wherein the NES comprises an inlet guard slot, a PHY-preamble slot, a MAC header slot, and an outlet guard slot.
29. The TDMA frame structure as claimed in claim 24, wherein each data slot comprises an inlet guard slot, a PHY-preamble slot, a MAC header slot, a slot for carrying traffic data, and an outlet guard slot.
30. The TDMA frame structure as claimed in claim 24, wherein the plurality of control slots comprises 1 NES and 16 NCS, and wherein the plurality of data slots comprises 28 data slots.
31. The TDMA frame structure as claimed in claim 24, wherein duration of each of the plurality data slots and each of plurality of the control slots is 2 ms.
32. The TDMA frame structure as claimed in claim 24, wherein total duration of the TDMA frame structure is 90 ms.
33. The TDMA frame structure as claimed in claim 24, wherein duration of the TDMA frame structure is dependent upon an update rate, number of nodes, a codec type, a voice latency requirement, a radio range, frequency hopping rate, and throughput.
34. The TDMA frame structure as claimed in claim 24, wherein an update rate is about 10 Hz, number of nodes is equal to 16, a codec type is Mixed-Excitation Linear Predictive enhanced (MELPe), voice latency is less than 120 ms, a radio range is about 40 Km, frequency hopping rate is 500 hops, and throughput is 1Mbps.
35. The TDMA frame structure as claimed in claim 24, wherein each of the plurality of data slots comprises an inlet guard slot of 270 µs duration, a slot of 1547 µs duration for carrying payload data, and an outlet guard slot of 183 µs duration.
36. The TDMA frame structure as claimed in claim 24, wherein each of the plurality of control slots comprises an inlet guard slot of 270 µs duration, a slot of 1547 µs duration for carrying control information, and an outlet guard slot of 183 µs duration.
37. A Network Control Slot (NCS) structure for incorporation in a TDMA frame structure, the NCS structure comprising:
an inlet guard slot;
a PHY-preamble slot;
a MAC header slot;
a slot for carrying MAC control information (MCI);
a slot for carrying time critical tactical messages;
a slot for carrying routing control packets;
a slot for application signalling messages; and
an outlet guard slot.
,TagSPECI: DESCRIPTION
TECHNICAL FIELD OF INVENTION
The invention generally relates to mobile self-forming networks. More particularly, the invention relates to dynamic TDMA medium access control structure for 1-Mbps self-forming radio network.
BACKGROUND OF INVENTION
Mobile self-forming radio network also known as Mobile Ad hoc NETworks (MANET) are known for their speedy and ease of deployment. Such networks are developed due to their inherent capability to support survivability, which is an essential requirement of the tactical environment. The tactical radio waveform is mainly governed by a Medium Access Protocol (MAC) protocol and a physical link technology enabling digital data to be transferred from one source to other destinations through a communication channel. To enable the sharing of a channel in a broadcasting wireless channel among other radio nodes, an efficient MAC protocol is required.
One approach for MAC design is use of contention based protocols such as ALOHA, CSMA/CA or DCF, while another approach is to use the Time Division Multiple Access (TDMA) protocol, where each node transmits or receives at given time slots. Such TDMA protocols being a scheduled MAC protocol are potentially better suited to networks with heavy or unbalanced load. The TDMA MAC is also suited to tactical MANET environment because of its capability to support QoS, which is not guaranteed in contention protocols. In static TDMA schemes the node’s time slot gets wasted, when it does not have traffic to transmit.
The article titled “Analyzing Impact of TDMA MAC Framing Structure on Network Throughput for Tactical MANET Waveforms” by Bhupendra Suman, LC Mangal, SC Sharma, published in Conference on Advances in Communication and Control Systems 2013 (CAC2S 2013) describes a typical design for dynamic TDMA frame structure.

OBJECT OF INVENTION
It is an object of the invention to identify important parameters which affect the frame structure design of a practical dynamic TDMA MAC and develop an interrelationship between the identified parameters.
It is yet another object of the invention to provide a mechanism that economizes the channel bandwidth needed in a mobile self-forming radio network.
It is yet another object of the invention to achieve greater capacity and enhanced delay performance in a mobile self-forming radio network.
SUMMARY OF INVENTION
In accordance with the purposes of the invention, as embodied and broadly described herein, the invention includes designing and developing network waveforms to meet the tactical communication requirements. One of critical network waveforms is UHF 1 Mbps MANET waveform, which is targeted to provide 1 Mbps network throughput to user application under MANET environment in Ultra-High Frequency (UHF) 225-512 MHz band. The waveform design addresses the primary requirement to support subnet size of 16 radio nodes, update rate 10Hz, and support for data and voice communication including MELPe with upper bound of voice latency 120ms for one hop range of 40Km. It also supports multihop distribution of all services. Frequency hopping support for 500 hops per second is an essential ECCM feature. This waveform design economizes the channel bandwidth needed in the MANET. To achieve greater capacity and enhanced delay performance in the MANET, the dynamic TDMA scheme is employed at the MAC layer.
In one embodiment, the invention includes a TDMA based device (1000), the device (1000) comprising: a processor (1001) to process a dynamic TDMA signal; and a transceiver (1003) to transmit and/or receive the dynamic TDMA signal, wherein each frame of the dynamic TDMA signal comprises a plurality of data slots and a plurality of control slots, wherein the plurality of control slots comprises at least one Network Control Slot (NCS), and wherein the at least one NCS comprises: (i) an inlet guard slot, (ii) a PHY-preamble slot, (iii) a MAC header slot, (iv) a slot for carrying MAC control information (MCI), (v) a slot for carrying a payload for higher layer control (vi) an outlet guard slot.
In one embodiment, the slot for carrying the payload for higher layer control comprises one or more of a slot for carrying time critical tactical messages, a slot for carrying routing control packets, and a slot for application signalling messages.
In one embodiment, the slot for carrying time critical tactical messages, the slot for carrying routing control packets, and the slot for application signalling messages are utilized according a predefined priority.
In one embodiment, the at least one NCS comprises a 270 µs slot for the inlet guard slot, a 1547 µs slot for carrying control information, and a 183 µs slot for the outlet guard slot.
In one embodiment, the PHY preamble has size of 128 bits, the MAC header has size of 80 bits, and the MCI has size of 320 bits.
In one embodiment, the slot for carrying a payload for higher layer control has a combined size of 1921 bits.
In one embodiment, the MAC header, the MCI, the time critical tactical messages, the routing control packets, and the application signalling messages are Forward Error Correction (FEC) encoded.
In one embodiment, the plurality of control slots further comprises a Network Entry Slot (NES).
In one embodiment, the NES comprises a 270 µs slot for a first guard time distribution, a 1547 µs slot for carrying control information, and a 183 µs slot for a second guard time distribution.
In one embodiment, the control information comprises a PHY preamble, a MAC header, and MCI.
In one embodiment, the PHY preamble has a size of 128 bits, the MAC header has a size of 80 bits, and the MCI has a size of 320 bits.
In one embodiment, the MAC header and the MCI are FEC encoded.
In one embodiment, each of the plurality of data slots comprises a 270 µs slot for a first guard time distribution, a 1547 µs slot for carrying payload data, and a 183 µs slot for a second guard time distribution.
In one embodiment, the payload data comprises a PHY preamble, a MAC header, and traffic data.
In one embodiment, the PHY preamble has size of 128 bits, the MAC header has size of 80 bits, and the traffic data has size of 2241 bits.
In one embodiment, the MAC header and the traffic data are FEC encoded.
In one embodiment, the plurality of control slots comprises a Network Entry Slot (NES) and 16 Network Control Slot (NCS), and wherein the plurality of data slots comprises 28 data slots.
In one embodiment, duration of each of the plurality of data slots and each of the plurality of control slots is 2 ms.
In one embodiment, total duration of the each frame is 90 ms.
In one embodiment, the device (1000) meets one or more requirements of - an update rate less than 10 Hz, number of nodes equal to 16, a codec type of Mixed-Excitation Linear Predictive enhanced (MELPe), voice latency less than 120 ms, a radio range about 40 Km, frequency hopping rate of 500 hops, and throughput about 1Mbps.
In one embodiment, the dynamic TDMA signal meets the requirements of UHF 1Mbps MANET waveform.
In one embodiment, the device further comprises a memory (1002) to store the dynamic TDMA signal; and an antenna (1004) to convert the dynamic TDMA signal into a radio signal and vice versa.
In one embodiment, the device (1000) is capable of communicating with a 1-Mbps self-forming radio network (1100).
In one embodiment, the invention includes a TDMA frame structure, comprising: a plurality of data slots; and a plurality of control slots having at least one Network Control Slot (NCS), wherein the at least one NCS comprises: (i) an inlet guard slot, (ii) a PHY-preamble slot, (iii) a MAC header slot, (iv) a slot for carrying MAC control information (MCI), (v) a slot for carrying a payload for higher layer control, and (vi) an outlet guard slot.
In one embodiment, the slot for carrying the payload for higher layer control comprises one or more of a slot for carrying time critical tactical messages, a slot for carrying routing control packets, and a slot for application signalling messages.
In one embodiment, the slot for carrying time critical tactical messages, the slot for carrying routing control packets, and the slot for application signalling messages are utilized according a predefined priority.
In one embodiment, the plurality of control slots further comprises a Network Entry Slot (NES).
In one embodiment, the NES comprises an inlet guard slot, a PHY-preamble slot, a MAC header slot, and an outlet guard slot.
In one embodiment, each data slot comprises an inlet guard slot, a PHY-preamble slot, a MAC header slot, a slot for carrying traffic data, and an outlet guard slot.
In one embodiment, the plurality of control slots comprises 1 NES and 16 NCS, and wherein the plurality of data slots comprises 28 data slots.
In one embodiment, duration of each of the plurality data slots and each of plurality of the control slots is 2 ms.
In one embodiment, total duration of the TDMA frame structure is 90 ms.
In one embodiment, duration of the TDMA frame structure is dependent upon an update rate, number of nodes, a codec type, a voice latency requirement, a radio range, frequency hopping rate, and throughput.
In one embodiment, an update rate is about 10 Hz, number of nodes is equal to 16, a codec type is Mixed-Excitation Linear Predictive enhanced (MELPe), voice latency is less than 120 ms, a radio range is about 40 Km, frequency hopping rate is 500 hops, and throughput is 1Mbps.
In one embodiment, each of the plurality of data slots comprises an inlet guard slot of 270 µs duration, a slot of 1547 µs duration for carrying payload data, and an outlet guard slot of 183 µs duration.
In one embodiment, each of the plurality of control slots comprises an inlet guard slot of 270 µs duration, a slot of 1547 µs duration for carrying control information, and an outlet guard slot of 183 µs duration.
In one embodiment, the invention includes a Network Control Slot (NCS) structure for incorporation in a TDMA frame structure, the NCS structure comprising: an inlet guard slot; a PHY-preamble slot; a MAC header slot; a slot for carrying MAC control information (MCI); a slot for carrying time critical tactical messages; a slot for carrying routing control packets; a slot for application signalling messages; and an outlet guard slot.
These and other embodiments of the invention will be described below in detail with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
To further clarify advantages and features of the invention, a more particular description of the invention will be rendered by reference to specific embodiments thereof, which is illustrated in the appended drawings. It is appreciated that these drawings depict only typical embodiments of the invention and are therefore not to be considered limiting of its scope. The invention will be described and explained with additional specificity and detail with the accompanying drawings in which:
Figure 1 illustrates a dynamic TDMA frame structure as per prior art.
Figure 2 illustrates a TDMA frame with NES as per prior art.
Figure 3 illustrates a physical slot structure as per prior art.
Figure 4 illustrates an exemplary plot for slot duration vs. physical bit rate.
Figure 5 illustrates an exemplary TDMA frame structure for the 1 Mbps Radio Network, in accordance with an embodiment of the invention.
Figure 6 illustrates an exemplary guard time distribution with in TDMA slot, in accordance with an embodiment of the invention.
Figure 7 illustrates an exemplary data slot structure, in accordance with an embodiment of the invention.
Figure 8 illustrates an exemplary NCS Structure, in accordance with an embodiment of the invention.
Figure 9 illustrates an exemplary NES Structure, in accordance with an embodiment of the invention.
Figure 10 illustrates an exemplary architecture of a node/device in the dynamic TDMA network implementing the TDMA frame structure for the 1 Mbps Radio Network, in accordance with an embodiment of the present invention.
Figure 11 illustrates a block diagram of an illustrative network system which employs the TDMA frame structure, in accordance with an embodiment of the present invention.
It may be noted that to the extent possible, like reference numerals have been used to represent like elements in the drawings. Further, those of ordinary skill in the art will appreciate that elements in the drawings are illustrated for simplicity and may not have been necessarily drawn to scale. For example, the dimensions of some of the elements in the drawings may be exaggerated relative to other elements to help to improve understanding of aspects of the invention. Furthermore, the one or more elements may have been represented in the drawings by conventional symbols, and the drawings may show only those specific details that are pertinent to understanding the embodiments of the invention so as not to obscure the drawings with details that will be readily apparent to those of ordinary skill in the art having benefit of the description herein.
DETAILED DESCRIPTION
For the purpose of promoting an understanding of the principles of the invention, reference will now be made to the embodiment illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated system, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates.
It will be understood by those skilled in the art that the foregoing general description and the following detailed description are exemplary and explanatory of the invention and are not intended to be restrictive thereof. Throughout the patent specification, a convention employed is that in the appended drawings, like numerals denote like components.
Reference throughout this specification to “an embodiment”, “another embodiment” or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. Thus, appearances of the phrase “in an embodiment”, “in another embodiment” and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment.
The terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process or method that comprises a list of steps does not include only those steps but may include other steps not expressly listed or inherent to such process or method. Similarly, one or more devices or sub-systems or elements or structures proceeded by "comprises... a" does not, without more constraints, preclude the existence of other devices or other sub-systems.
The overall TDMA MAC structure design involves two phases. First is frame structure design and second is slot structure design. The frame structure design involves consideration of network size, throughput, jitter considerations and service latency requirements. The slot design needs to consider guard time and frequency hopping (FH) dwell time as FH is essential requirements for ECCM in hostile tactical environment.

Dynamic TDMA Frame Structure Design (as per Prior Art)
The dynamic TDMA protocol divides the channel into network control slots (NCS) and data slots as shown in Figure 1 (Prior Art). The NCS are for sharing the network control information necessary to dynamically assign the traffic data slots (interchangeably data slots).
The data slots are dynamically allotted to the radio nodes based on their traffic need and priority. The dynamic TDMA protocol exploit the spatial reuse of the radio channel for data slots to enhance the channel bandwidth efficiency, while the control slots are statically assigned to the radio nodes to support QoS. In tactical environment the number of nodes keeps joining or leaving the network due to mobility, therefore some fixed numbers of net entry slots (NES) are also required in TDMA MAC frame as shown in Figure 2 (Prior Art).
In this structure the bits sent in data traffic slots only contributes to the application throughput, while the NES and NCS are the overhead, essential to manage the dynamism of the network. In such frame structure to support a large number of radio nodes, it is desirable to keep the frame duration sufficiently large to minimize overhead due to NES and NCS. The number of NES is fixed in a design and the number of NCS is network size dependent parameter, required by each node for exchanging its management information and for traffic slot negotiations. Therefore, if the frame duration is kept large, it adversely affects the latency requirements of control as well as of user traffic. Since the latency requirements for critical communication services are predefined for most of the tactical application, the frame duration can be decided on that basis. The network degree and throughput, increases the physical channel data rate requirements. The higher physical data rate puts constraints on radio modem design and RF channel bandwidth as well as such signals are more susceptible to noise as a small change in signal amplitude or phase may cause the receiver to misjudge the received data.

TDMA Slot Structure Design (as per Prior Art)
To design the TDMA slot structure, it is essential to consider the impact of guard time per slot or TX burst on network throughput. The guard time is required to cater for propagation delay, clock synchronization mismatch, radio processing delay, frequency tuning time, TX/RX switching, power amplifier (PA) ramp up and PA ramp down along with their uncertainties. In addition to this, the slot duration must be kept sufficiently large to accommodate channels coded MAC frame plus PHY preamble as shown in Figure 3 (Prior Art).
The Equation (1) for the MAC payload (x), which directly contributes the throughput of the network, is:
x=[(S-g).R_b-p] F_r-M_h …..(1)
Where:
S => Duration of a TDMA slot
g => Guard time
R_b => Channel data rate
p => Preamble in bits
F_r => Channel coding rate
M_h => MAC header size
The guard time and other overheads significantly affect the effective throughput of the network. The guard time elements depend on hardware components like PA ramp up and PA ramp down etc. The major element of guard time is the propagation delay, which varies during the operation of the network. Indeed, it depends on the relative position of the communicating radio nodes.

TDMA Structure Design for 1 Mbps Radio Network (as per Invention)
The prior art as explained in conjunction with Figures 1-3 considers only the payload of traffic slot for throughput calculation. However, in practical implementation, the control information size is quite less compared the size of network control slots. It is therefore, desirable to have smaller duration of the NCS. However, reducing the NCS duration increases the relative overhead due to fixed guard time. Further, it is also not possible to reduce transmission duration smaller than one FH dwell time.
To effectively utilize the NCS bandwidth capacity, the traffic of critical timing nature and other important network management traffic of higher layers may be included in the NCS as per the invention. This concept of including such traffic into the NCS, in addition to effectively utilizing NCS bandwidth also improves the following two design aspects:
Apt and assured delivery of time critical tactical messages as the periodicity of NCS transmission for every node is well-defined and guaranteed.
Quick broadcasting of control packets of higher layers as they, now don’t need to go through resource reservation phase of dynamic TDMA protocol. It helps better convergence time for network. It makes overall system more responsive.
Since, now the NCS, apart from control information also carries traffic data, the above Equation (1) for throughput gets revised to the Equation (2) given below:
T_h=(M+N)/(M+N+L)[R_(b ).F_r-1/S {g.R_b.F_r+p.F_r+M_h+(M.M_c)/(M+N)}] …..(2)
Where:-
T_h => Nework throughput
L => Number of NES slots
M => Number of NCS Slots
N => Number of Traffic Data Slot
M_C => NCS Control Payload Size in bits
S => Duration of a TDMA slot
g => Guard time
R_b => Channel data rate
p => Preamble in bits
F_r => Channel coding rate
M_h => MAC header size
It is evident form the Equation (2) that the network throughput, T_h is directly proportional to channel data rate R_(b ). A good design needs to aim to provide maximum throughput for minimum possible channel data rate meeting all the user requirements. In the above equation guard time g is limited by range of communication and available hardware technology, which affects the PA ramp up/ramp down time, etc. The parameters like T_h,? M?_h, M_c,M,and N are governed by the user networking requirements. Therefore for better throughput slot time S and channel data rate R_(b )can be optimized considering the requirements of update rate of the network, which is given below in the Equation (3) below:
T_f=(L+M+N).S …..(3)
Figure 4 illustrates an exemplary graph between channel data rate R_(b ) and slot time S for 1 Mbps throughput. It is deduced from the plot, that increasing the slot size, relaxes the requirement of high physical channel data rate, keeping all other parameters constant. There are two knee points in the plot which can give optimum slot duration for the following two cases:
Case 1: The slot duration of 3 ms is optimum choice for the case where, relatively less physical data rate is of prime importance, for all other the parameters keeping the same. The selection of this slot duration, however does not meet the requirements of compatibility with frequency hopping rate of 500 hops per second.
Case 2: The second knee point for slot duration of 2 ms is optimum choice for the case where the frame duration can be kept 90 ms. The selection of this slot duration will require relatively more physical data rate with respect to case 1, keeping all other the parameters same. However, it meets all the given design requirements.
Hence, to meet the requirements of UHF 1 Mbps MANET waveform, the TDMA MAC frame is designed of duration 90 milli-second (ms). The frame duration of 90ms meets the constraints of voice latency and update rate. The selected frame duration is also able to provide jitter free MELPe communication and is compatible with frequency hopping rate of 500hops.
The 90ms TDMA frame is further divided into 1 Network Entry Slot (NES), 16 Network Control Slots (NCS) and 28 Data Slots each of duration 2ms. This TDMA frame also called TDMA Cycle as it repeats after every 90ms as shown in Figure 5.
Since in this design the requirement of 1 Mbps throughput is already given, the physical channel data rate is calculated first, then the required MAC payload can be find out to support the required throughput.
Applying the equations, the channel data rate is calculated as R_(b )= 1.958 Mbps for the parameter values as shown in Table 1 below:
Sr.# Parameters Value
1 Network throughput, T_h 1 Mbps
2 Number of NES Slot, L 1
3 Number of Traffic Data Slot, N 28
4 Number of NCS Slot , M 16
5 NCS Control Payload Size in bits, M_C 80 Bits
6 Duration of a TDMA slot, S 2 ms
7 Guard time, g 453 µs
8 Preamble in bits, p 128 Bits
9 Channel coding rate, F_r 0.8
10 MAC header size, M_h Ceil(N/8)* 80 Bits
Table 1: Design Parameters

Data Slot Structure Design Details (as per Invention)
The slot structure design needs to consider the guard time to calculate effective time available for transmission. For the waveform the radio range is 40Km. After the guard time distribution, the time available for data transmission in 2ms slot is 1547µs as shown in Figure 6.
The value of various guard elements is shown in Table 2 below.
Guard Time Elements Value (micro second)
Propagation Delay 133
Sync Time jitter 50
Frequency Tuning Time 20
Tx/Rx Switching Time 100
PA Ramp Up Time 100
PA Ramp Down Time 50
Table 2: Guard Time Elements

The detailed structure of the data slot is shown in Figure 7.
The values of various fields are listed in Table 3 below:
Sr.# Traffic Data Slot fields Value (bits)
1 PHY Preamble 128
2 MAC Header 80
3 Traffic Data 2241
Table 3: Traffic Data Slot Size

Control Slot Structure Design Details (as per Invention)
The NCS and NES and are the control slots. The NCS are the time slots used by each node to exchange its MAC Control Information (MCI), which mainly contains bitmaps for distributed data slot scheduling and timing information for network synchronization. The structure of NCS is shown in Figure 8.
The values of various fields of NCS are listed in Table 4 below:
Sr.# Traffic Data Slot fields Value (bits)
1 PHY Preamble 128
2 MAC Header 80
3 MCI 320
4 Higher Layer Control
(Time Critical Messages, Routing Control Packets, Application Signalling Messages) 1921
Table 4: NCS Size

The size of various payloads of “Higher Layer Control” is kept variable limited to the maximum space available after PHY Preamble, MAC Header and MCI. In the case, where all these are queued for transmission and the required size is more than space available, for such a case, priority is assigned to these payloads as shown in Table 5 below:

Sr.# Traffic Data Slot fields Priority
1 Time Critical Messages 0
2 Routing Control Packets 1
3 Application Signalling Messages 2
Table 5: Prioritization of NCS payloads

Here, lower number indicates the higher priority value for transmission. This design is a generic one as more payloads can be added in future with appropriate priority values.
The other control packet is NES. This packet is being used by the new radio node to send its net joining control packet to existing network nodes to acquire a conflict free NCS. The structure of NES is shown in Figure 9. The NES requires only basic fields of NCS viz. PHY Preamble, MAC Header and MCI. The values of these fields are same as of NCS.
Figure 10 illustrates an exemplary architecture of a node/device 1000 implementing the dynamic TDMA frame structure for the 1 Mbps Radio Network. Examples of such devices include, but are not limited to devices used in - a telecommunication network, a software defined radio (SDR) network, a Free Space Optical (FSO) network, a sensor network, a satellite communication network. In one specific example, the device 1000 may be a mobile phone and a base station. The device 1000 contains one or more processors 1001, a memory 1002, and a transceiver 1003. Each transceiver 1003 including a transmitter (Tx) or other transmitting means known in the art (not shown) for transmitting data to the other transceivers of the network 1100 via a corresponding antenna 1004. Transceivers further include a receiver (Rx) or other receiving means known in the art (not shown) for receiving data from the other transceivers via its corresponding antenna 1004. A module is stored in the memory 1002 and executed by the one or more processors 1001 to generate the TDMA frame structure described in conjunction with the Figures 5 to 9. The transceiver 1003 is configured to transmit and receive control and data packets necessary to implement the TDMA frame structure for the 1 Mbps Radio Network. Those skilled in the art will appreciate that other hardware and/or software configurations are also possible here.
Figure 11 illustrates a block diagram of an illustrative in a network system 1100 implementing the dynamic TDMA frame structure. Examples of the network systems include, but are not limited to telecommunication network, satellite systems, combat-net radio systems, and PON networks. In one example, the network system 1100 is the 1 Mbps self-forming Radio Network. The network system 1100 comprises devices 1000-1 to 1000-n, each including circuitry or like hardware (not shown) as is known in the art for implementing the dynamic TDMA frame structure at the MAC layer of the devices 1000-1 to 1000-n. In one embodiment, the MAC protocol is run or is otherwise executed on an embedded processor (not shown) within each of the devices 1000-1 to 1000-n. While the figure illustrates a wireless network system, the dynamic TDMA frame structure of the present invention may also be utilized with various other communication systems.
In this way, the design of dynamic TDMA medium access control structure for 1-Mbps self-forming radio network is carried out in order to meet the objective of developing technology for medium access in wireless environment. This design is successfully implemented for UHF 1 Mbps MANET waveform of Software Defined Radio (SDR). The main advantages of the invention include the following: Identification and theoretical formulation of parameters contributing to the design of TDMA frames structure; Development of a systematic approach of TDMA frame structure design; and Bandwidth efficient structure design of Network Control Slots by incorporating the controls of higher layers and time critical tactical traffic.
While certain present preferred embodiments of the invention have been illustrated and described herein, it is to be understood that the invention is not limited thereto, but may be otherwise variously embodied and practiced within the scope of the following claims.