Link aggregation, or multi-band striping, has been used in wireless backhaul systems to overcome the limitations of bandwidth and transmission range. Work-conserving and in-sequence delivery are essential but conflicting requirements in multi-band striping systems. Previous schemes can achieve one or the other, but not both. The heterogeneous channel and time varying data rate in multi-band wireless backhaul systems present additional challenges. We aim at designing a multi-band striping algorithm to achieve both work-conserving and in-sequence delivery in the heterogeneous time-varying multi-band wireless backhaul system. We propose a parallel processing architecture for multi-band aggregation, and derive the necessary conditions for such system to achieve sequence preserving and work conserving. An optimum set of timing controls is developed and proved to provide the best performance. We design a work-conserving in-sequence striping algorithm and prove it to be sequence preserving and work conserving. The algorithm is then extended to practical data granularity. Performance analysis and simulation results demonstrate that our designs are able to preserve data sequence, reduce delay, and achieve 100% channel utilization. © 2002-2012 IEEE.