Vehicular Ad hoc Networks (VANET) consist of radio-equipped vehicles and roadside units (RSU) and support many safety and commercial applications. Multi-hop forwarding can extend the communication range of both RSUs and vehicular broadcasts. Recently, the use of Positive Orthogonal Codes (POC) as transmission patterns of repetition-based broadcast medium access control (MAC) for safety messages has been proposed. This thesis proposes a cooperative forwarding protocol in which multiple relays at each forwarding hop form a virtual relay and coordinate their transmission times to correspond to a POC codeword. The protocol thereby exploits spatial diversity while conforming to the POC-based MAC, resulting in fewer collisions and mitigating the effect of hidden terminals. The design is validated through NS2 simulations, which show comparable performance with other forwarding schemes while producing significantly less performance degradation for safety message broadcasts on the same channel.

Vehicular Ad hoc Networks (VANET) consist of radio-equipped vehicles and roadside units (RSU) and support many safety and commercial applications. Multi-hop forwarding can extend the communication range of both RSUs and vehicular broadcasts. Recently, the use of Positive Orthogonal Codes (POC) as transmission patterns of repetition-based broadcast medium access control (MAC) for safety messages has been proposed. This thesis proposes a cooperative forwarding protocol in which multiple relays at each forwarding hop form a virtual relay and coordinate their transmission times to correspond to a POC codeword. The protocol thereby exploits spatial diversity while conforming to the POC-based MAC, resulting in fewer collisions and mitigating the effect of hidden terminals. The design is validated through NS2 simulations, which show comparable performance with other forwarding schemes while producing significantly less performance degradation for safety message broadcasts on the same channel.

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Multihop routing is an effective method for establishing connectivity between the nodes of a network. End-to-end outage probability and total power consumption are applied as the optimization criteria for routing protocol design in multihop networks based on the local channel state information measurement at the nodes of a network. The analysis shows that employing instantaneous channel state information in routing design results in significant performance improvement of multihop communication, e.g., achieving full diversity order when the optimization criterion is outage performance. The routing metrics derived from the optimization problems cannot be optimized in a distributed manner. Establishing an alternate framework, the metrics obtained are converted into new composite metrics, which satisfy the optimality and convergence requirements for implementation in distributed environments. The analysis shows that the running time of the proposed distributed algorithm is bounded by a polynomial. / Communications

The next generation of cellular networks is expected to carry high speed IP traffic in a packet switched environment in order to accommodate data traffic for a wide range of services. Much research is thus focused on how to increase the transmission rate in cellular networks. A general consequence of increasing transmission rate in a radio link is a corresponding increase in transmit power, resulting in increased interference and reduced network capacity. The straightforward way to reduce this effect is to shorten the link distance, which in the cellular case means shrinking the cells. This, however, means increased control traffic for handoffs and location registration, as well as increased infrastructure costs. An alternative approach, which has received increased attention lately, is the introduction of wireless multihop access networks to relay traffic between the wired infrastructure and the users. Such an access network must clearly accommodate all types of services expected to operate in next generation systems, including real-time services. However, wireless multihop networks have traditionally had problems meeting the delay requirements posed by such services. In this thesis, we will study the delay performance through analysis and simulation of such a network, based on the Virtual Cellular Network proposal [1], in which geographically fixed wireless relays are deployed to act as both network nodes and user relays. / Nästa generations mobilnät förväntas bära paketväxlad höghastighetstraffik för att kunna stödja en stor mängd varierande tjänster. Mycket forskning har däför fokuserat på transmissionshastigheten i mobilnäten. En generell konsekvens av att öka transmissionshastigheten i ett radiobaserat nätverk är en motsvarande ökning i transmissionsstyrkan, vilket resulterar i ökad interferens och följaktligen minskad kapacitet. En lösning på det problemet är att minska avståndet mellan sändare och mottagare, vilket i fallet med dagens mobila infrastruktur innebär mindre, och fler celler. Detta skulle dock innebära både ökad kontrolltraffik och större kostnader för planering och underhåll av infrastruktur. En alternativ väg, som den senaste tiden fått ökad uppmärksamhet, är införandet av ett trådlöst vidarebefordrande accessnätverk mellan de mobila stationerna och det fasta nätet. Ett sådant nätverk måste naturligtvis kunna ackommodera samtliga typer av tjänster som förväntas utnyttja nästa generations mobilnät, inklusive realtidstjänster. Dock har kraven på låg fördröjning hos denna typ av tjänster traditionellt inneburit problem problem för vidarebefordrande trådlösa nätverk. I denna rapport studeras fördröjningskaraktären hos ett sådant nätverk, baserat på konceptet Virtual Cellular Network [1], i vilket geografiskt fixerade radionoder vidarebefordrar traffik mellan mobila stationer och det fasta nätet.

LoRaWAN is one of the most adopted low-power wide-area networks, which use theproprietary LoRa modulation developed by Semtech to provide high sensitivity at lowdata rates for long ranges. LoRaWAN providing coverage using single-hop gatewaysto thousands of end-devices (sensors) running on batteries. Each gateway requires aconnection to the internet or a private network (Ethernet, 3G/4G, Wifi) to communicatewith the network server. In obstructed areas, with mountains, foliage, or simplyvast areas, multiple gateways are required to provide coverage for the end-devices.Internet/mobile coverage might be missing in some areas. Which quickly brings upthe cost of internet connection in these areas, unless a solution is developed that routesmessages between the gateways using the existing LoRa radio communication standard.Thus reducing required internet connections while providing coverage. This solutionwas developed and evaluated, with a focus on supporting LoRaWAN deviceswith bidirectional capabilities, following the regional regulations, and providing arouting protocol that minimizes the extra data that comes with routing messages overa network. Experiments of three gateways showed that the solution provides a functioningrouting protocol, with as low as 3 extra bytes for routing. While fast enough toprovide bidirectional communication support for end-devices located farthest awayfrom the gateway with the server connection.

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