Bridge Architecture – Revolutionizing Dual Mode 4G Cellular Modem Dongle Design
In the continued drive to keep consumers wherever they are, the connected cellular network has been an invaluable enabler. 3G and 4G connectivity, initially restricted to cell phones, is now widely available for laptops as well. Initially a niche market for the on-the-go business person, cellular connectivity for laptops is currently experiencing explosive growth due to college students and the new generation of latte-drinking employees.
Devices that enable cellular connectivity for laptops are known by a variety of names, including mobile broadband devices and laptop connection cards, among others, depending on the carrier you talk to. As data revenue gets bigger and bigger in every carrier’s revenue pie, so does the growth in popularity of Cellular Modem Dongles. Currently, all major cell phone carriers offer a full line of such devices for sale. These modem dongles range from the simplest 3G connectivity to modems with added features such as SD expandability and even dual-mode modems. These modem dongles offer only the ability to connect to the cellular network for data needs. These devices are dedicated data transmitting and receiving devices that mainly consist of an RF chip, a baseband modem, and a power management IC.
When it comes to dual-mode modem dongles, a few possibilities come to mind. They are:
1.GSM+CDMA modem
2. 3G+4G cellular modem
3. Cellular Modem + WiFi
GSM+CDMA
In most cellular markets today, there is a mix of standards. The two main cellular standards of GSM and CDMA could work for operators by tying subscribers to limited networks. However, this often limits consumers, especially in developing countries where different operators have better coverage in their own locality. Therefore, just like the rise of dual-mode cell phones in those countries, dual-mode modem dongles will see the same growth.
3G + 4G Cellular
Another currently popular CMD design is a combination of 3G and 4G modems. These designs take advantage of the high-profile 4G mobile data service and the more widely available 3G data service. With most carriers today choosing either WiMax or LTE as their preferred 4G implementation, modem dongles are beginning to incorporate them into their design while supporting more prevalent 3G connectivity.
Cellular Modem + Wi-Fi
A third design option is the cellular modem and WiFi dongle. Although WiFi may be standard on many laptops today, the new 802.11n standard is not yet built into computers. Also, due to carrier specifications, many carrier-bound netbooks will not have WiFi capability. This will create the need for an additional device capable of providing WiFi connectivity when available and still keep the operator’s data revenue stream intact.
USB performance
USB performance is another key factor in dual-mode modem design. Since USB is the predominant interconnection between the modem and the PC, it is essential that the system’s USB capability is operating at full capacity. After all, why have a modem capable of delivering more than 100 Mbps of data if your system’s USB capacity is limited to around 80 Mbps?
This is another vital factor that puts bridge chips at the forefront of these systems. Unlike a hub that only passes through the USB data coming from the modems, the bridge chips can connect to other higher-performance interfaces on the modems (for example, the memory interface). This allows the modem to transmit as much data as possible and not be affected by the modem’s built-in USB performance.
They are:
1. Independent data paths
2. Flexible interfaces
3. Size
Independent data paths
This feature is useful for dual-mode cellular modem dongles due to tight power consumption restrictions. Given the 500mA power limitation, it is vital that modems be able to constantly switch between different power modes to keep the system in balance. This allows for the ability to constantly switch without upsetting the fragile balance of the system or interrupting the flow of data.
flexible interfaces
Bridge chips also provide more flexible interfaces within a design, allowing developers to add an additional SD card or change memory interfaces. This flexibility gives designers the freedom to easily swap features across their system while maintaining a fast time-to-market for their design.
Size
Many bridge chips are designed specifically for mobile devices. Its size is much smaller compared to hubs that are normally designed for computer peripherals. This is an added benefit for a mobile device like a USB stick, as size does matter. The smaller a CMD is, the easier it is to transport. By using bridging architectures, developers can enable the dongle to meet all the necessary specifications of a dual-mode cellular modem dongle while enabling additional enhancements and functionality.
Know more…