Currently proposed 3G systems offer roaming, higher capacity and increased flexibility for low bandwidth services, such as voice calls and messaging. While future wireless systems (4G and higher) are envisioned to provide higher capacity, they are also expected to support heterogeneity in the following aspects:

• Physical environments (ranging from high-bandwidth low error-rate pico-cells to low-bandwidth high error-rate macro-cells)
• Network architectures (cellular, peer-to-peer, or other hybrid network models)
• Applications (ranging from low data-rate non-real-time applications to high data-rate real-time applications)