## 1 Introduction  
The smart grid (SG) aims to address most of the shortcomings of the existing electrical grid by integrating information and communication technologies to improve its performance. SG implementation will involve a set of communication networks that allow SG sub-systems, such as the advanced metering infrastructure (AMI), to integrate a number of devices and technologies to enable improvement in the electric power system in terms of reliability, efficiency, economics and environment. This ambitious modernisation of the electrical grid is only feasible by dint of a seamless integration between devices and technologies, which include:  
* smart meters at the consumer end,* two-way communication networks at different infrastructures,
* data management systems and
* software application platforms to interface with utilities' control end. In terms of reference design, the IEEE-2030-2011 standard [1] provides architectural perspectives to support interoperability among SG system components, which broadly includes power and Information and Communications Technology (ICT) domains. Within the communication domain, the standard further provides a set of guidelines on communication networks, protocols and media to interconnect functional blocks, such as generation, transmission and distribution in the power domain. From the implementation perspective, the Communications Technology (CT) specifies three levels of network, namely [2]: Home Area Network (HAN), Neighbourhood Area Network (NAN) and Wide Area Network (WAN). In the NAN, traffic sources, such as smart meters, are required to collect time-based data for real-time, reliability-sensitive applications from consumers. This information is then transmitted through available communication networks to the data concentrator or utility control centre [3]. The static multi-hop Wireless Mesh Network (WMN) is a promising communication technology for enabling AMI applications. However, due to the nature of SG and the challenges of interference and channel errors associated with IEEE 802.11 [4] wireless channels, efficient routing protocols are necessary to drive optimal packet delivery in a bid to meet or surpass the traffic QoS of AMI applications over WMN. Quality-of-service (QoS) is the capability of a network to provide certain features in terms of delay, reliability, bandwidth and availability. Due to the complexities of SG traffic and the constraints of wireless networks, it has become essential to retrofit QoS components in the conventional WMN to satisfy the high reliability requirement of SG applications [5]. The varying SG application traffic types in NAN may have different constraints for QoS, such as latency, bandwidth and packet delivery. This raises the need for QoS-aware routing in smart meters that will be deployed as mesh nodes in WMN-based NANs. QoS differentiation in existing communication networks is normally achieved through resource reservation, traffic classification and prioritization. Specifically, various approaches can be employed to prioritize important delay-critical data over loss-critical data. For instance, many MAC layers (e.g., 802.11e and 802.16) support the specification of different traffic categories, and they use scheduling algorithms to provide bandwidth differentiation [6; 7]. However, MAC-based solutions are generally limited to providing QoS guarantees on single communication links, which also requires further enhancement to be effective in multihop scenarios, such as WMN-based NANs [8]. The multiple hop capability in WMN is achieved through routing protocols, which rely strictly on the link metrics to select the best paths to destinations. Packets for different applications may also be lost, altered or delayed during transmission as a result of congestion, protocol errors or link disruptions. Therefore, adopting suitable mechanisms to enforce QoS guarantees on different network flows based on the constraints and requirement of SG application traffic is crucial to achieving a high level of communication reliability.