Rome, February 14, 2013 Status of the Project Report on the first year activities With the support of the Prevention, Preparedness and Consequence Management of Terrorism and other Security-related Risks Programme European Commission - Directorate-General Home Affairs

Summary  Network Issues  MAC Techniques  HFTP  DCHF  Possible Scenarios (Logical Topology)  Token passing  Contention based  Mixed  Comparison between HFTP and DCHF  Model  Analytical Results  SWING simulations  Voice transmission  Data transmission  Conclusions CNIT-Siena

Considering the topology of the high-survival HF radio network, and according to its general requirements and communication scenarios, each ECI only communicates with its home CGA. This means that ECI to ECI communication is not required (even within the same area), and data exchange between different areas involves just CGA-to-CGA communication. Consequently, single-hop communication is always considered and no routing functionalities are really needed. In this case, the main network issues concern Medium Access Control (MAC) layer aspects, which are crucial to allow possible concurrent transmissions in the system. Network issues CNIT-Siena

MAC Techniques HFTP Wireless Token Ring Protocol  WTRP is a token bus protocoll, derived from IEEE 802.4;  Efficient medium access control in hevily loaded networks  Appropriate for networks that experience significant packet loss rates and relatevely long link turnaround times;  SOLLICIT_SUCCESSOR and SET_SUCCESSOR mechanism for dropping and adding nodes to the network  Token Relay  Merging Rings DCHF Distributed Coordination Function  Contention-based scheme based on the popular wireless MAC protocol, IEEE DCF with some features incorporated from MACAW (Multiple Access with Collision Avoidance for Wireless);  Physical carrier sensing and the DIFS delay are not used;  After successful channel acquisition, the backoff range is halved rather than reset to the minimum;  Data packets carry the size of the sending node’s contention window, which is then used by all nodes. CNIT-Siena

Possible scenarios Token passing Scenario In this scenario, each node that needs to transmit (either ECI or CGA), waits for token reception. Upon receiving the token, it is allowed to try to transmit its packet for a limited time interval (usually set long enough for the specific network), before releasing the token. In the considered solution, the token passes through all nodes of the network by means of a logical ring covering the entire network. CNIT-Siena

Possible scenarios Contention based Scenario This scenario does not need the design of any logical ring. Indeed, in this case we assume that every node uses a DCHF MAC scheme to get channel access. More precisely, the transmitting node senses the channel and establishes a connection, either using a RTS/CTS procedure or not, with the receiving node. CNIT-Siena

Possible scenarios Mixed Scenario This scenario represents a compromise between the first two cases. In particular, we distinguish between two different kinds of communications: ECI-CGA and CGA- CGA. Assuming that heavy traffic conditions may occur only in the former case, we select a contention free mechanism for ECI-CGA communications and a contention- based scheme for CGA-CGA communications. CNIT-Siena

Comparison HFTPDCHF The performance of a MAC protocol could be analyzed by evaluating three main metrics: Average Latency per Packet: it is the total delay suffered by a packet from the time it arrives at a node until the time it gets transmitted on the channel. This metric identifies the responsiveness of the protocols for varying traffic conditions. Channel Utilization: it is the fraction of total time the channel is being utilized to transmit bits, and it is a measure of the efficiency of these protocols. Saturation Throughput: is measured under the condition that every node in the network constantly tries to send traffic. This metric measures how well the MAC protocol handles heavy traffic The network consists of N nodes Mean packet arrival rate: λ pck/s Mean service rate: μ pck/s Mathematical model - M/G/1 queue CNIT-Siena

Comparison ChanelServiceTime = T success + T fail (1/P success – 1) T success and T fail represent respectively the time taken for a successful transmission and the total time in case of failed channel acquisition; P success is the probability of successful acquisition of the same; T q is the time spent by a packet in node’s buffer, known as Queueing Delay; ρ is the traffic intensity. DCHF Tcycle is the average time taken for the token to complete one full rotation in the ring; Tq is the time spent by a packet in node’s buffer, known as Queueing Delay; Tpkt is the mean time taken to transmit one packet in the channel; Tt is the link turnaround time; b token is the dimension in bit of the token HFTP CNIT-Siena

Analytical results Input Data: N = 4; rate = 6400 bit/s DCHF packet = 30 bytes HFTP token = 40 bytes ACK = 30 bytes Packet = 320 bytes Link Turnaround = 1 ms CNIT-Siena

Analytical results Input Data: N = 4; rate = 6400 bit/s DCHF packet = 30 bytes HFTP token = 40 bytes ACK = 30 bytes Packet = 320 bytes Link Turnaround = 1 s CNIT-Siena

Input Data: N = 4; rate = 6400 bit/s DCHF packet = 30 bytes HFTP token = 40 bytes ACK = 30 bytes Packet = 320 bytes Analytical results CNIT-Siena

TRANSMISSIONPARAMETERINPUT Digital Voice Mode I Packet320 B Rate2634 b/s Digital Voice Mode II Packet320 B Rate5620 b/s Data Mode I Packet320 B Rate6400 b/s Data Mode II Packet1000 B Rate9600 b/s SWING Simulations The behavior of the analytical model has been evaluated for voice and data transmissions. The simulation results are obtained by implementing the mathematical model in Matlab ® for different values of the input parameters. CNIT-Siena

Conclusions In order to provide a complete design of the SWING system, we have investigated the requirements related to network layer operations. We highlighted that end-to-end communications in the SWING scenario are most of the times confined to single-hop communications, i.e., from ECIs to CGAs or among CGAs. Such consideration led us to focus our research activity on MAC layer aspects, which are crucial to allow possible concurrent transmissions in the system. Short link turnaround time: independently of the mode and type of data managed, the contention based technique DCHF shows better performance with respect to the contention free mechanism consequence of the introduction of an overhead in the token management heavier than the double handshake mechanism used for DCHF connection establishment. Long turnaround time: the HFTP exhibits improved performance than DCHF. The main reason for such a behavior lies in the different weight of the double handshake in DCHF, that causes a double turnaround, with respect to the token overhead, which is able to generate a single turnaround per passage/transmission. In HF communications the realization of a network with a long turnaround time is more feasible, we may conclude that a medium access control technique without contention based on a token protocol seems to be a suitable solution for the implementation of the SWING network. The use of a token-based mechanism to avoid contention might affect the delay in case of a single node transmission. SWING network topology: an internet failure caused by a terrorist attack will unlikely involve a single ECI and, rather, it will probably cause the contemporary access of several nodes to the SWING network. CNIT-Siena

Conclusions DeliverablesOwnerDeadlines 2 - Technical analysis of the communication problems related to the identification and designation of CIs in the interested area INGV M1 – M9 Sept 2012 Technical Report 3 - Determination of the topology of high survival radio communication network CNIT M1 – M9 Sept 2012 Technical Report 6 - Analysis of the existing architecture of HF communication based on internet protocol access with reference to the above considered infrastructures CNIT M1 – M6 Jun2012 Technical Report 8 - Definition of the high survival HF radio network technical requirements CNIT M1 – M6 Jun2012 Technical Report 9 - Radio network system designCNIT M1 – M12 Dec 2012 Technical Report