  This paper is the first extensive work on total order reliable convergecast
in multi-hop Wireless Body Area Networks (WBAN). Convergecast is a many-to-one
cooperative scheme where each node of the network transmits data towards the
same sink. Our contribution is threefold. First, we stress existing WBAN
convergecast strategies with respect to their capacity to be reliable and to
ensure the total order delivery at sink. That is, packets sent in a specific
order should be received in the same order by the sink. When stressed with
transmission rates up to 500 packets per second the performances of these
strategies decrease dramatically (more than 90% of packets lost). Secondly, we
propose a new posture-centric model for WBAN. This model offers a good
characterization of the path availability which is further used to fine tune
the retransmission rate thresholds. Third, based on our model we propose a new
mechanism for reliability and a new converge-cast strategy that outperforms
WBAN dedicated strategies but also strategies adapted from DTN and WSN areas.
Our extensive performance evaluations use essential parameters for WBAN: packet
lost, total order reliability (messages sent in a specific order should be
delivered in that specific order) and various human body postures. In
particular, our strategy ensures zero packet order inversions for various
transmission rates and mobility postures. Interestingly, our strategy respects
this property without the need of additional energy-guzzler mechanisms.
