# Moving Towards Body-to-Body Sensor Networks for Ubiquitous Applications: A Survey
## 3 BBN Design Considerations
### QoS-Aware Traffic Management for BBN
Each player submit its own QoS requirements within the contention free period. A Cournot model was then proposed to share fairly the network resources between the WBAN players. The WBAN traffic priorities are reported by Figure 4. Upon simulations, it was observed that the utility function of the WBAN player increases proportionally to the throughput and conversely to the delay, in accordance with the Cournot model. In [63], authors proposed a multi-constrained MAC protocol (McMAC) with energy-aware QoS provisioning that supports WBANs heterogeneous traffic. Delay and reliability are considered as the most important QoS metrics in a WBAN. McMAC classifies the intra-WBAN traffic into five classes, based on the delay and the reliability: emergency traffic with hard QoS constraints (life-critical situations), soft QoS traffic with acceptable reliability and delay (electrocardiogram for example), high reliability traffic with no delay constraint (respiration monitoring), high delay traffic with no reliability constraint (telemedicine video streaming applications), and finally non-constrained traffic like the human physiological information (temperature, respiration rate, etc.). The McMAC protocol introduces the \"transmit-whenever-appropriate\" superframe structure, a novel superframe structure based on principle which guarantees multi-constrained QoS. Either in the contention access period or contention-free period, the WBAN nodes and coordinator handle the emergency packets and ensure an energy-efficient delivery with minimum delay and maximum reliability. Only single-hop transmissions are performed by McMAC, which is almost enough for intra-WBAN communications, but multi-hop is necessary for inter-WBANs scenarios in BBNs. The problem of single-hop and minimum hop encountered in LRPD and McMAC, was resolved by [64], using the two-hop extension of the IEEE 802.15.6 standard. Then, a QoS control scheme in a multi-hop WBAN is proposed to optimize the energy efficiency, the packet delivery failure ratio (PDFR) and the number of transmissions instead of the delay. The solution in [65] consists of a random contention based resource allocation (RACOON) protocol that ensures QoS for multiple WBANs with mobility management. RACOON is a bandwidth control mechanism integrated into a MAC layer. To ensure the multi-WBAN QoS, RACOON has two major features. First, it utilizes a centralized control scheme, by the central processing node (CPN), to minimize energy consumption of WBANs, to prevent inter-WBAN interference and packet collisions. RACOON also implements a probing-based inter-WBAN interference detection scheme to decrease energy waste in the WBANs, which simplifies QoS controls. To this end, RACOON uses two channels: one is intended to negotiate the sharing of network resources, the other is for the transmission of polling messages and sensing data between the sensors and CPN. Second, RACOON implements an iterative bandwidth control mechanism with respect to users' priorities, so that high priority WBANs get better bandwidth than low priority WBANs. The main advantage of the RACOON protocol is that it considers a multi-WBAN design, with inter-WBAN interference and inter-WBAN priorities considerations, based on polling messages. Moreover, RACOON deals with WBANs mobility, collisions and the energy waste that may result. This could be a promising protocol for BBNs to define each WBAN priority with respect to his energy and service requirements. Nevertheless, RACOON should support inter-WBANs communications and the related specific QoS and mobility requirements to apply to BBNs. A comparison of the aforementioned protocols is given by Figure 5.  
Figure 4: WBAN traffic priorities according to [62].