The next step in the never-ending hunt for faster data rates in cellular networks occurred recently. Rohde & Schwarz and Samsung announced the first test of LTE-A (LTE-Advanced) downlink carrier aggregation.
Downlink Carrier Aggregation lets several wireless providers share a transmission channel. Defined in 3GPP Release 10, carrier aggregation is a technology whereby up to five carriers, 20-MHz wide, can share a 100-MHz wireless data channel using frequency-division multiplexing (Figure 1).
Figure 1. LTE-A carrier aggregation creates a 100-MHz bandwidth from five 20-MHz channels.
3GPP Release 10 defines three types of carrier aggregation:
- Intra-band contiguous carrier aggregation
- Intra-band non-contiguous carrier aggregation
- Inter-band non-contiguous carrier aggregation
Figure 2 gives examples of carrier aggregation. Testing carrier aggregation in LTE-Advanced network infrastructure explains the concept in more detail.
Figure 2. Carrier aggregation combines inter-channel and intra-channel contiguous and non-contiguous bands, each 20-MHz wide.
The need for carrier aggregation stems from the fact that wireless providers are assigned 20-MHz bands of the electromagnetic spectrum. But, that leave can gaps of unused spectrum because a service provider's carriers aren't contiguous. Carrier aggregation fills those gaps so that one base station can transmit and receive carriers from different service providers, making better use of available spectrum.
According to the announcement, the test was performed on a Samsung internal test device containing a Samsung SHANNON300 modem chipset as the DUT. A Rohde & Schwarz LTE-Advanced-capable CMW500 wideband radio communication tester performed the test.
Carrier aggregation is just one technology needed to bring 1 Gbit/s downlink data rates to every mobile device. The complete package of what will be the real 4G wireless technology (as opposed to what service providers marketing departments have termed 4G) will come when wireless devices and base stations use (MIMO) multiple-input multiple-output technology. MIMO uses multiple antennas to maximize radio signals, thus increasing bandwidth and data rates over today's single antenna systems.
Are you involved with testing upcoming wireless technologies? Share your experiences with us.