21-07-2012, 01:20 PM
RF Aspects and Challenges
[attachment=28335]
How Advanced is LTE Advanced? – RF Aspects & Challenges
LTE became a commercial reality in 2010 following the launch of many LTE networks using 3G/LTE multimode devices. LTE Advanced is the next major milestone in the evolution path, encompassing 3GPP Rel. 10, 11 and beyond.
In order to achieve higher data rates while preserving compatibility with older LTE standards, the designers of LTE-Advanced had to use some relatively advanced techniques. Larger amounts of radio frequency spectrum may be utilized in addition to new techniques for more efficient use of limited spectrum. Devices compatible with the new technology are likely to feature a number of antenna arrays, and a process called beam-forming can turn would-be interference into a tool to boost signal.
Carrier Aggregation
Using a scheme known as carrier aggregation, a cellular base station can break apart a stream of data and transmit it through multiple radio frequencies to a user’s device, which then reassembles these multiple pieces into the original data stream.
• Support wider transmission bandwidths up to 100MHz
• Two or more component carriers (CC) are aggregated
• A terminal may simultaneously receive one or multiple component carriers depending on its capabilities
• Possible to aggregate a different number of component carriers of possibly different bandwidths in the UL and the DL In typical TDD deployments, the number of component carriers and the bandwidth of each component carrier in UL and DL will be the same.
• Both Intra and Inter band carrier aggregation are considered as potential Tx RF scenarios and parameters and cover both of; Contiguous Component Carrier and non-contiguous Component Carrier aggregation
Enhanced uplink multiple access
LTE-Advanced enhances the uplink multiple access scheme by adopting clustered SC-FDMA, also known as discrete Fourier transform spread OFDM (DFT-S-OFDM). This scheme is similar to SC-FDMA but has the advantage that it allows noncontiguous (clustered) groups of subcarriers to be allocated for transmission by a single UE, thus enabling uplink frequency-selective scheduling and better link performance. Clustered SC-FDMA was chosen in preference to pure OFDM to avoid a significant increase in PAPR. It will help satisfy the requirement for increased uplink spectral efficiency while maintaining backward-compatibility with LTE.
LTE Advanced UE Receivers and Categories
The following aspects to be defined considering the CA scenarios, bandwidth of the Tx/Rx signals as well as multiple antenna effects:
• Receiver Sensitivity
• Selectivity
• Blocking performance
• Spurious response
• Intermodulation performance
• Spurious emission
The existing UE categories 1-5 for Release 8 and Release 9 are shown in below table.
Challenges of LTE-Advanced
3GPP's Long Term Evolution (LTE) is the leading technology standard for 4G wireless communications. Although it is just now being launched commercially, development of the standard continues, with the latest version being LTE-Advanced. With enhancements such as a 1Gbps peak data rate, LTE-Advanced will meet International Telecommunication Union (ITU) requirements for the International Mobile Telecommunications (IMT)-Advanced 4G radio-communication standard.
The current release of LTE already meets most IMT-Advanced requirements. Exceptions are peak data rate and uplink spectral efficiency, which LTE-Advanced addresses via wider bandwidths, enabled by carrier aggregation, and higher efficiency, enabled by enhanced uplink multiple access and enhanced multiple antenna transmission (advanced MIMO).
[attachment=28335]
How Advanced is LTE Advanced? – RF Aspects & Challenges
LTE became a commercial reality in 2010 following the launch of many LTE networks using 3G/LTE multimode devices. LTE Advanced is the next major milestone in the evolution path, encompassing 3GPP Rel. 10, 11 and beyond.
In order to achieve higher data rates while preserving compatibility with older LTE standards, the designers of LTE-Advanced had to use some relatively advanced techniques. Larger amounts of radio frequency spectrum may be utilized in addition to new techniques for more efficient use of limited spectrum. Devices compatible with the new technology are likely to feature a number of antenna arrays, and a process called beam-forming can turn would-be interference into a tool to boost signal.
Carrier Aggregation
Using a scheme known as carrier aggregation, a cellular base station can break apart a stream of data and transmit it through multiple radio frequencies to a user’s device, which then reassembles these multiple pieces into the original data stream.
• Support wider transmission bandwidths up to 100MHz
• Two or more component carriers (CC) are aggregated
• A terminal may simultaneously receive one or multiple component carriers depending on its capabilities
• Possible to aggregate a different number of component carriers of possibly different bandwidths in the UL and the DL In typical TDD deployments, the number of component carriers and the bandwidth of each component carrier in UL and DL will be the same.
• Both Intra and Inter band carrier aggregation are considered as potential Tx RF scenarios and parameters and cover both of; Contiguous Component Carrier and non-contiguous Component Carrier aggregation
Enhanced uplink multiple access
LTE-Advanced enhances the uplink multiple access scheme by adopting clustered SC-FDMA, also known as discrete Fourier transform spread OFDM (DFT-S-OFDM). This scheme is similar to SC-FDMA but has the advantage that it allows noncontiguous (clustered) groups of subcarriers to be allocated for transmission by a single UE, thus enabling uplink frequency-selective scheduling and better link performance. Clustered SC-FDMA was chosen in preference to pure OFDM to avoid a significant increase in PAPR. It will help satisfy the requirement for increased uplink spectral efficiency while maintaining backward-compatibility with LTE.
LTE Advanced UE Receivers and Categories
The following aspects to be defined considering the CA scenarios, bandwidth of the Tx/Rx signals as well as multiple antenna effects:
• Receiver Sensitivity
• Selectivity
• Blocking performance
• Spurious response
• Intermodulation performance
• Spurious emission
The existing UE categories 1-5 for Release 8 and Release 9 are shown in below table.
Challenges of LTE-Advanced
3GPP's Long Term Evolution (LTE) is the leading technology standard for 4G wireless communications. Although it is just now being launched commercially, development of the standard continues, with the latest version being LTE-Advanced. With enhancements such as a 1Gbps peak data rate, LTE-Advanced will meet International Telecommunication Union (ITU) requirements for the International Mobile Telecommunications (IMT)-Advanced 4G radio-communication standard.
The current release of LTE already meets most IMT-Advanced requirements. Exceptions are peak data rate and uplink spectral efficiency, which LTE-Advanced addresses via wider bandwidths, enabled by carrier aggregation, and higher efficiency, enabled by enhanced uplink multiple access and enhanced multiple antenna transmission (advanced MIMO).