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[Â÷¼¼´ëÀ̵¿Åë½Å] LTE ÀÌÁßÁ¢¼Ó(Dual Connectivity) ±¸Á¶ Ç¥ÁØÈ
½º¸ô¼¿ ¼º´ÉÇâ»ó(Small cell enhancement) »óÀ§°èÃþ Ãø¸é(Higher Layer aspect) Ç¥ÁØÈ
3GPP(3rd Generation Partnership Project)´Â WCDMA, LTE, LTE-Advanced µî Åë½ÅÇ¥Áر԰ÝÀ» Á¦Á¤ÇÏ´Â ±¹Á¦Ç¥ÁØÈ ´ÜüÀÌ´Ù. 3GPP¿¡¼´Â Release-12¿¡ ´ëÇÑ Ç¥ÁØÈ ÀÛ¾÷À» ÁøÇà ÁßÀÌ´Ù. Release-12 Ç¥ÁØÈ ÀÛ¾÷ Áß¿¡ ±âÁ¸ÀÇ ¸ÅÅ©·Î ±âÁö±¹(Macro eNB)¿¡ ºñÇÏ¿© ¸Å¿ì ÀÛÀº Áö¿ªÀ» Ä¿¹öÇϵµ·Ï ÇÏ´Â ½º¸ô ±âÁö±¹(Small eNB)¿¡ ´ëÇÑ Å¸´ç¼º¿¬±¸(Feasibility Study)¸¦ ¿Ï·áÇϰí 2014³â 4¿ù ÇöÀç Ç¥ÁØÈ ÀÛ¾÷¾ÆÀÌÅÛ(Work Item)À» ÁøÇà ÁßÀÌ´Ù. ½º¸ô¼¿ ¼º´ÉÇâ»ó Ç¥ÁØÈ ÀÛ¾÷¾ÆÀÌÅÛ Áß LTE¿¡¼ÀÇ ÀÌÁßÁ¢¼Ó(Dual connectivity) ±¸Á¶¿¡ ´ëÇÑ Ç¥ÁØÈ´Â »ç¿ëÀÚ Ãø¸é¿¡¼ÀÇ Àü¼Û·ü(Throughput) Áõ´ë°¡ °¡´ÉÇϵµ·Ï ÇÏ´Â ¹æ¾ÈÀÌ¸ç »óÀ§°èÃþÃø¸éÀ» ³íÀÇÇÏ´Â 3GPP TSG RAN WG2 ¿¡¼ ÁÖµµÀûÀ¸·Î Ç¥ÁØÈ ÁøÇà ÁßÀÌ´Ù.
LTE ¿¡¼ÀÇ ÀÌÁßÁ¢¼Ó(Dual connectivity) ±¸Á¶
±âÁö±¹Àº Ä¿¹öÇÏ´Â ¿µ¿ªÀÇ Å©±â¿¡ µû¶ó¼ ¸ÅÅ©·Î(Macro), ÇÇÄÚ(Pico), ÆèÅä(Femto) ±âÁö±¹ µîÀ¸·Î ±¸º°µÈ´Ù. ¸ÅÅ©·Î ±âÁö±¹Àº ÇÇÄÚ(Pico), ÆèÅä(Femto) ±âÁö±¹ µî¿¡ ºñÇÏ¿© ³ÐÀº ¿µ¿ªÀ» Ä¿¹öÇϱâ À§ÇÏ¿© »ç¿ëÇÒ ¼ö ÀÖ´Â ±âÁö±¹ÀÌ´Ù. 3GPP¿¡¼´Â ÇÇ·Î(Pico) ȤÀº ÆèÅä(Femto) ±âÁö±¹ µîÀº ½º¸ô ¼¿(Small cell)·Î ĪÇϰí ÀÖ´Ù. ¸ÅÅ©·Î¿Í ½º¸ô ±âÁö±¹ÀÌ È¥ÀçÇÏ´Â »óȲ¿¡¼ º¸´Ù È¿À²ÀûÀ¸·Î ³×Æ®¿öÅ©¸¦ È¿À²ÀûÀ¸·Î »ç¿ëÇÒ ¼ö ÀÖ´Â ´Ù¾çÇÑ ¹æ¾È¿¡ ´ëÇÏ¿© ¿¬±¸°¡ ÁøÇà ÁßÀÌ´Ù.
LTE¿¡¼ÀÇ ÀÌÁßÁ¢¼Ó(Dual Connectivity) ±¸Á¶´Â ´Ü¸»ÀÌ RRCÁ¢¼Ó(RRC connected) »óȲ¿¡¼ ºñÀÌ»ó¹éȦ(Non-ideal backhaul)À» ÅëÇÏ¿© ¿¬°áµÇ´Â Àû¾îµµ µÎ °³ ÀÌ»óÀÇ ¼·Î ´Ù¸¥ ³×Æ®¿öÅ© ³ëµå(Master¿Í Secondary eNB ȤÀº Macro¿Í Small eNB)µé¿¡¼ Á¦°øµÇ´Â ¹«¼±ÀÚ¿ø(Radio resource)À» »ç¿ëÇÏ´Â ¹æ½ÄÀ» ÀǹÌÇÑ´Ù. ¹Ý¼ÛÆÄ Áý¼º(Carrier aggregation) ¹æ½ÄÀÌ ±âÁö±¹°ú RRH µîÀÌ ¿¬°á ½Ã¿¡ Àü¼ÛÁö¿¬ ½Ã°£ÀÌ °ÅÀÇ °í·ÁµÇÁö ¾Ê¾Ò´ø »óȲ¿¡ ºñÇÏ¿© ÀÌÁßÁ¢¼Ó ±¸Á¶(Dual Connectivity)¿¡¼´Â ±âÁö±¹ °£¿¡ Àü¼Û½Ã°£ Áö¿¬ µîÀ» °í·ÁÇÏ¿©¾ß ÇÏ´Â »óȲÀÌ´Ù. ÀÌÁßÁ¢¼ÓÀ» ÅëÇÏ¿© ´Ü¸»Àº »ç¿ëÀÚ Ãø¸éÀÇ Àü¼Û·ü(throughput) Áõ´ë¸¦ À§ÇÏ¿© ¹«¼±ÀÚ¿øÀ» Áý¼ºÇÏ´Â ¹æ½Ä¿¡ ´ëÇÏ¿© ³íÀÇ Áß¿¡ ÀÖ´Ù.
ÀÌÁßÁ¢¼Ó(Dual connectivity) ±¸Á¶ Ç¥ÁØÈ ³íÀÇ ÇöȲ
ÀÌÁßÁ¢¼Ó ±¸Á¦¿¡ ´ëÇÑ Å¸´ç¼º ¿¬±¸(Feasibility Study) °úÁ¤À» °ÅÃļ ¼·Î ´Ù¸¥ ±âÁö±¹ °£¿¡ ¹«¼±ÀÚ¿ø Á¢¼ÓÀ» À§ÇÑ °¡Àå À¯·ÂÇÑ ³×Æ®¿öÅ© ±¸Á¶¸¦ °áÁ¤ÇÏ¿´À¸¸ç À̸¦ ¹ÙÅÁÀ¸·Î ¼·Î ´Ù¸¥ ±âÁö±¹ °£¿¡ ¹«¼±ÀÚ¿ø Áý¼ºÀ» À§ÇÑ ´Ù¾çÇÑ ¹æ¾È¿¡ ´ëÇÑ ³íÀǰ¡ ÁøÇà Áß¿¡ ÀÖ´Ù.
2014³â 4¿ù 3GPP TSG RAN WG2#85bis ½ºÆäÀÎ ¹ß·»½Ã¾Æ ȸÀǸ¦ ÅëÇÏ¿© ÀÌÁßÁ¢¼Ó Áö¿øÀ» À§ÇÑ ±âº»ÀûÀÎ ½Ã±×³Î¸µ ±¸Á¶¿¡ ´ëÇÏ¿© ³íÀÇÇÏ¿´´Ù.
¿¹¸¦ µé¸é, ´Ü¸»ÀÇ À̵¿¼º(Mobility)À» °í·ÁÇÏ¿© ¸¶½ºÅÍ ±âÁö±¹(Master eNB, MeNB)°ú ÀÌÂ÷±âÁö±¹(Secondary eNB, SeNB)À» º¯°æÇϱâ À§ÇÑ ½Ã±×³Î¸µ¿¡ ´ëÇÏ¿© ³íÀÇÇÏ¿´´Ù.
(Ãâó: R2-141537, Mobility procedures for dual connectivity, Ericsson)
<±×¸² 1>À» ÅëÇÏ¿© ÀÌÂ÷±âÁö±¹(SeNB)ÀÌ º¯°æµÉ °æ¿ì¿¡ ½Ã±×³Î¸µ °úÁ¤¿¡ ´ëÇÏ¿© ³íÀÇÇÏ¿´´Ù. ³íÀǸ¦ ÅëÇÏ¿© ½º¸ô¼¿ ±×·ì¿¡ ´ëÇÑ º¯°æ(Modification)¿¡ ´ëÇÑ ½Ã±×³Î¸µ°ú À¯»çÇÑ ¹æ½ÄÀÌ »ç¿ëµÉ °ÍÀ» °áÁ¤ÇÏ¿´´Ù. ¶ÇÇÑ ¸¶½ºÅͱâÁö±¹(MeNB)Àº RRC Àç¼³Á¤(Reconfiguration) ¸Þ½ÃÁö¸¦ ´Ü¸»¿¡ Àü¼ÛÇÔÀ¸·Î½á ¼Ò½º ±âÁö±¹(source eNB)À» ÇØÁ¦(release)ÇÒ ¼ö ÀÖµµ·Ï °áÁ¤ÇÏ¿´´Ù. ¹Ý¸é¿¡, ¸¶½ºÅͱâÁö±¹(MeNB)ÀÌ ÀÌÂ÷±âÁö±¹(SeNB)¿¡°Ô ÇØÁ¦(release)¸¦ ¸í·ÉÇÏ°Ô µÉ °æ¿ì¿¡ ÀÌ¿¡ ´ëÇÑ ÀÀ´äÀÌ ÀÌÂ÷±âÁö±¹(SeNB)·ÎºÎÅÍ ÇÊ¿äÇÑÁö µî »ó¼¼ÇÑ ³»¿ëÀº 3GPP TSG RAN WG3ÀÇ °áÁ¤¿¡ µû¸£±â·Î ÇÏ¿´´Ù.
¸¶½ºÅͱâÁö±¹(MeNB)ÀÇ º¯°æ¿¡ µû¸¥ ±âÁö±¹ °£¿¡ RRC ¸Þ½ÃÁö´Â ±âÁ¸¿¡ ¸¶½ºÅͱâÁö±¹(MeNB) °£¿¡ ÇÚµå¿À¹ö¿¡ »ç¿ëµÇ´Â ¸Þ½ÃÁö¸¦ »ç¿ëÇÒ ¼ö ÀÖµµ·Ï °áÁ¤ÇÏ¿´´Ù.
¶ÇÇÑ »óÇ⸵ũ Àü¼Û ½Ã¿¡ ÇϳªÀÇ º£¾î·¯(bearer)¸¦ ¸ÅÅ©·Î¿Í ½º¸ô¼¿ ¾çÂÊÀ¸·Î ºÐ¸®ÇÏ¿© Àü¼ÛÇÏ´Â ¹æ½Ä¿¡ ´ëÇÏ¿© ³íÀÇÇÏ¿´´Ù. ÇÏÁö¸¸, »óÇ⸵ũ º£¾î·¯ ºÐ¸® Àü¼ÛÀÇ °æ¿ì º¹À⼺°ú Ç¥ÁØÈ ÀÏÁ¤À» °í·ÁÇÏ¿© Relase-12¿¡¼´Â °í·ÁÇÏÁö ¾Ê°í ÇâÈÄ ÀÌÁßÁ¢¼Ó ±¸Á¶ÀÇ Ãß°¡ÀûÀÎ ¼º´ÉÇâ»ó µîÀÇ Ç¥ÁØÈ¿¡¼ ³íÀÇÇϱâ·Î ÇÏ¿´´Ù.