In this paper, we study the joint spectrum allocation and scheduling problems with the objectives of maximizing throughput and achieving certain fairness in Dynamic Spectrum Access (DSA) wireless networks. A novel Multi-Channel Contention Graph (MCCG) is proposed to characterize the impact of interference under the protocol interference model. Based on MCCG, we present an optimal scheme to compute maximum throughput solutions. As simply maximizing throughput may result in a severe bias on resource allocation, we take fairness into consideration by presenting optimal schemes to compute fair solutions based on a simplified max-min fairness model and the well-known proportional fairness model. Fast and effective heuristics are also proposed to provide high throughput and fair solutions. Numerical results show that compared with the optimal schemes, our heuristic schemes produce very close performance and our proportional fair schemes achieve a good tradeoff between throughput and fairness. In addition, we extend our research to the physical interference model.