# Moving Towards Body-to-Body Sensor Networks for Ubiquitous Applications: A Survey
## 3 BBN Design Considerations
### QoS-Aware Traffic Management for BBN  
The applications targeted by the design of the BBN should benefit from high quality communications, that should be ensured by a QoS-aware inter-WBAN routing protocol. Such protocol should then fulfill stringent QoS requirements by defining an application-dependent QoS-aware routing metrics. The QoS-aware peering routing protocol for reliability (QPRR) is proposed in [59]. QPRR uses end-to-end QoS and redundant paths to ensure reliability in the WBAN. Authors showed, by simulating real hospital scenarios, that QPRR performs effectively for both stationary and mobile patients. They classified the devices used in WBAN communications into three energy-based classes: Nursing Station Coordinator (NSC), which is directly connected to the power source, medical display coordinator (MDC), which uses replaceable batteries, and WBAN coordinator, which has limited energy availability. The simulations of QPRR protocol verify successful transmission rate, reduced traffic load, energy consumption and latency. The QPRR reliability is above 88% for low density stationary WBANs and 75% for mobile WBANs. The scalability is also ensured for a large number of nodes and the reliability is above 74%. However, QPRR is an infrastructure-based network, which is a major limitation in a BBN distributed system where WBANs play independently the role of sources and destinations. Besides, neither bandwidth consideration is made in the route selection, nor fault detection. Indeed, the reliability of the WBAN link with his neighbor is evaluated upon receipt of transmission acknowledgments, the protocol is unable to detect congestion or predict link disconnections. In a subsequent study [40], the same authors improved the QPRR protocol by adding a delay module and implementing an enhanced version of the protocol referred as ZEQoS, which integrates energy and QoS-aware modules. The targeted application of the new protocol is the hospital indoor service and the WBAN sensor data is classified into : ordinary packets (OPs), delay-sensitive packets (DSPs) and reliability-sensitive packets (RSPs). The path selection mechanism of ZEQoS improves the throughput for all data types, since it calculates the communication costs of all possible paths and selects the best path that fulfills the QoS demands. ZEQoS also provides good achievements of throughput, with reduced overhead and packet loss than comparable protocols, namely the Data-centric multiobjective QoS-aware routing protocol (DMQoS) [60]. Despite the QoS considerations, no energy and no mobility management are involved in ZEQoS; only static topology is assumed and the overlapping issue is tackled for fixed WBANs. The model could be extended to a BBN scenario to minimize the interference between neighboring WBANs, with more specific investigations, especially with traffic priorities compliant to the BBN application. For instance, military QoS is different from sport team QoS, and QoS mapping schemes are needed in case of heterogeneous BBN scenarios, where WBANs could use different transmission technologies. It is worth to cite another recent work [61] that focuses on the delay as the ultimate QoS parameter to optimize. Authors propose a lightweight routing protocol for dynamic (LRPD) topology changes in WBANs. The sensor data are also classified according to delay priorities, into general packets (GP) and delay-sensitive packets (DP). The typical feature of LRPD is the decomposition of the total delay into the different delay components throughout the whole transmission process, i.e, queuing, transmission, propagation and procession delays are calculated and minimized consecutively. However, the major drawback of LRPD is the increased energy consumption due to the minimum hop routing used to forward DP packets. QoS parameters (throughput, delay and priority) have also been used in [62] as a utility function in a game-theoretical approach to resolve the overlapping issue of WBANs that coexist in a limited geographic area.