How Cellular 4G/5G Networks Work - Wireless Networks | Computer Networks Ep. 7.4 | Kurose & Ross

Summary

This video provides an in-depth explanation of how cellular 4G and 5G networks function, focusing on key aspects like architecture, mobility management, and the technologies behind them. It highlights the differences between cellular and Wi-Fi networks, the role of base stations, user authentication, and billing processes. The video also discusses advancements in 5G, such as increased bandwidth and the support for more devices in dense areas, introducing smaller cells called pico cells. The goal of 5G is to improve network capacity and performance in highly populated environments, offering a glimpse into the future of mobile internet.

Takeaways

• 😀 Cellular networks (4G and 5G) are the dominant mobile internet solution, covering densely populated areas with high bandwidth capabilities.
• 📱 User Equipment (UE) connects to base stations in a network of cells, each managing a specific geographic area with its own base station.
• 🌐 Mobile networks have a core network and an access network, which interconnects subscribers to the internet via an IP-based infrastructure.
• 🔑 Authentication is essential in cellular networks, as devices are identified by their IMSI number on SIM cards, which links them to specific user data and billing information.
• ⚙️ The packet core of mobile networks has evolved from separate voice and data services in 4G to a unified IP-based network in LTE and 5G.
• 📡 Mobile networks use tunneling protocols to allow devices to maintain their IP address while moving between different cells.
• 💡 In 5G, the addition of higher frequency bands allows for faster speeds but requires smaller cells (pico-cells) due to shorter signal range.
• 📶 The radio link layer and medium access control (MAC) in mobile networks handle data transmission reliability, channel usage, and time slot allocation.
• 🛠️ 4G and 5G networks differ in their ability to support more devices in dense areas, with 5G enabling more simultaneous connections and less congestion.
• 🌍 Mobile networks also allow for roaming between different carriers, where the 'home network' manages the user's service data and subscriptions.
• 🔋 Power management is a key aspect of mobile networks, allowing devices to enter light or deep sleep modes to save battery while still staying connected.

Q & A

What is the primary difference between cellular networks and Wi-Fi networks as mentioned in the video?

The main difference is that cellular networks are designed to provide mobile internet access across large areas and are capable of supporting many more devices simultaneously, especially in dense areas. In contrast, Wi-Fi networks are typically used for local area networks (LANs) and have a more limited range and capacity.

What does the term 'mobile network' refer to, and how is it structured?

The mobile network is a collection of interconnected networks that provide both voice and data services to users. It consists of a core network, an access network, and connections to the broader internet. The network is divided into multiple cells, each served by a base station, and users connect through these base stations.

What role does the International Mobile Subscriber Identity (IMSI) play in the cellular network?

The IMSI, stored on a device's SIM card, is a unique 64-bit identifier used to authenticate the device on the network. It allows the network to associate the device with a subscriber's identity and manage services, billing, and mobility across different network providers.

How do mobile networks handle mobility and ensure continuous service as users move between cells?

Mobile networks manage mobility through the coordination of base stations and the packet core. The mobility management entity (MME) keeps track of the user's real-time connection state, such as the cell they are connected to, and facilitates handoffs between cells to ensure uninterrupted service.

What is the significance of tunneling in mobile networks, and how does it work?

Tunneling in mobile networks allows user data to be securely transmitted through the core network as the device moves between cells. The data is encapsulated in an additional IP tunnel, ensuring that the user retains their IP address while passing through different subnets.

How does the mobile network differ from traditional LANs in terms of authentication and billing?

Mobile networks have stricter authentication and billing mechanisms compared to LANs. Each mobile device is authenticated by the base station, and the user's identity and usage are tracked for billing purposes. This ensures that unauthorized access is prevented and that services are charged correctly.

What new challenges does 5G aim to address compared to 4G?

5G aims to provide significantly higher bandwidth and better support for a larger number of devices in dense urban environments. It also introduces smaller cell sizes (pico cells) to accommodate high device density, addressing the limitations of 4G's ability to handle high traffic in crowded areas.

How do small cells (pico cells) in 5G networks differ from the larger cells used in previous generations?

Small cells, or pico cells, have a much smaller geographical coverage compared to the large cells used in 4G networks. They are used in high-density areas to provide better coverage and support for more simultaneous users. This requires the deployment of a larger number of base stations.

What is the function of the Serving Gateway (SGW) in a mobile network?

The Serving Gateway (SGW) acts as the entry point for the base station into the packet core, handling the initial connection setup between the user equipment and the mobile network. It facilitates the tunneling of user data towards the Packet Gateway (PGW) for internet access.

What are some of the components of the mobile network's data plane, and how do they function?

The data plane includes several layers, such as the Packet Data Convergence Layer (PDCL), the Radio Link Control (RLC), and the Medium Access Control (MAC) layer. These layers manage tasks like data compression, encryption, reliable data transfer, and efficient radio resource usage, ensuring smooth communication between devices and base stations.