1. A mast er radi o access network (RAN) node associate d with a maste r ra dio acce ss technology (R AT), the ma ster R AN no de comprisi ng: a memory; and at l east one processor coupled to the memory and configure d t o: com munica te with a seco ndary R AN node associate d w it h a secondary R AT a nd provide a ra dio term in al wit h dua l connect ivi ty that uses t he maste r RAT and the se condary RA T; and in response to rec eivi ng, f rom t he radi o te rminal or a c ore netwo rk, termina l capability inf orma ti on indicating tha t the radio termi nal supports a spl it beare r, u se a Packet Data Conve rgence Prot oc ol (PDCP) e ntit y for a maste r cel l group split be are r fo r the radio term inal, the PDCP entit y providing unifie d PDCP functi ona litie s, wh ere in the unified PDCP func tiona li tie s are used f or bot h t he master cell grou p s plit be are r an d a seconda r y c e ll group split bearer, the maste r cel l group split beare r is a use r plane bearer whose radio protoc ols a re spl it at t he ma ster RAN node a nd belong to both a maste r cell group provided by the mast e r RAN node an d a seconda ry cell grou p provide d by the sec onda ry RAN node , and the sec onda ry cell grou p s plit be are r is a user plane beare r wh ose radio p rotocols are spl it at t he se condary RAN node and be long to bot h t he sec ondary ce ll group a nd the maste r c ell group.

2. The ma ster R AN node acc ording to Claim 1, where in the un ifie d PDCP functiona lities a re common fu nctional ities that both fi rst PDC P f u nctio nalit ies correspond ing to the master R AT and secon d PDC P f u nctio nalit ies correspond ing to the sec ond a ry RAT have.

3. The ma ster R AN node acc ording to Claim 1, where in the un ifie d PDCP functiona lities a re a co mmon s ubse t between fi rst PDCP func ti onaliti e s corre sponding to the master RA T and se c ond PDC P func ti onaliti e s corre sponding to the secon dary R AT.

4. The ma ster R AN node acc ording to Claim 1, where in secon d PDCP func tiona li ties correspondi ng to the sec ondary RAT are a subse t of fi rst PD CP funct iona lit ies c orresponding to the master RAT, and the unified PDCP func tiona li tie s are the same a s, or a subse t of, the second PDCP func tiona lit ie s corresponding to the sec ondar y RAT.

5. The ma ster R AN node acc ording to an y one of C laims 1 to 4, wh ere in the at least one proce ssor is c onfig ured to prepare the PDC P enti ty that p rovides t he unifie d PDCP functionali ties by esta blis hing, re-es tablishi ng, or re configuri ng a PDC P entity with a c onf igurat ion common to both first PDCP fu nction a lities corre sponding t o t he m as te r RAT and second PDCP func tiona li ties cor respondi ng to the secondary RAT.

6. The ma ster R AN node acc ording to an y one of C laims 1 to 5, wh ere in the at least one processor i s confi gu re d to est a blish, re -e stabl ish, or rec onf igure a PDC P entit y fo r an alrea dy esta blishe d ma ster cell group bea rer, or to swi tch a mode of the PDCP e ntity for the master cell grou p bearer, in such a wa y that it provi de s t he unified PDCP func ti onaliti e s, th ere by est abli shing t he PDC P entit y t ha t provides the un ifie d PDCP functiona lities for the maste r cel l group split bearer, for the seconda ry ce ll group spl it be are r, or for a sec ondary cell group bea rer, whe re in the maste r cel l group be arer is a u se r pla ne beare r w hose radio protocol s are onl y locate d in t he maste r cell group, and the sec onda ry cell grou p bearer is a user plane beare r whose radio protoc ols a re only located in the secondary cell group.

7. The ma ster R AN node acc ording to an y one of C laims 1 to 5, wh ere in the a t lea st one pr ocessor is configured to, if t he ra di o term ina l support s a split bearer, use the P DCP entity that provides t he unifie d PDC P f u nctio nalit ies also for a ma st er cell group bearer for the radi o termi nal, regardless of whe ther the dua l connec tivi ty i s sta rted for the radio terminal, wherein the maste r cel l group be arer is a u se r pla ne beare r w hose radio protocol s are onl y locate d in t he maste r cell group.

8. A secon da ry ra dio access network (R AN) node confi gu re d t o support a seconda ry radio acc es s tec hnol ogy (R AT), the seconda ry RAN node comprising: a memory; and at l east one processor coupled to the memory and configure d t o: com munica te with a ma ster R AN n ode that supports a maste r RAT and p ro vide a radi o term inal wi th dual connecti vity tha t uses the master R AT a nd the secondary RAT; a nd if the m aste r RAN node rec e ive s, from the ra dio te rm inal or a core ne tw ork, term inal capa bilit y information indicat ing that t he radio terminal support s a spl it bea rer, use a Pa cke t Data Convergence Prot oc ol (PDCP) e ntit y for a seconda ry cell group s plit be arer for t he radio term inal, the PDCP entit y providing unifie d PDCP functi ona litie s, wh ere in the unified PDCP func tiona li tie s are used f or bot h t he secondary cell grou p s plit be are r an d a maste r cel l group split be are r, the maste r cel l group split beare r is a use r plane bearer whose radio protoc ols a re spl it at t he ma ster RAN node a nd belong to both a maste r cell group provided by the mast e r RAN node an d a seconda ry cell grou p provide d by the sec onda ry RAN node , and the sec onda ry cell grou p s plit be are r is a user plane beare r wh ose radio p rotocols are spl it at t he se condary RAN node and be long to bot h t he sec ondary ce ll group a nd the maste r c ell group.

9. A ra dio term ina l com prising: at l east one wi re le ss tra nsce ive r c onfi gured to comm unicate with bo th a maste r radi o a ccess netw ork (RAN) node a ss oci a ted wit h a maste r ra dio acce ss technology (R AT) a nd a seco ndary RA N node associat ed with a secondary RAT; a nd at l east one processor configure d to: perfo rm, via the at least one w ire le ss transce iver, d ua l connectivity th at uses the ma st e r RAT and the secondary RA T; if the radio te rm inal support s a split bea re r, t ra nsmit , to the maste r RAN node , te rm ina l capability info rmation indi cating t hat the radio t e rmi na l supp ort s a split be are r; a nd if the radio te rm inal support s a split bea re r, use a Pa cket Data C onvergence Prot oc ol (P DCP) e nti ty for a maste r cel l group split bea rer for the radi o termi nal, the PDCP e ntit y providing unifi e d PDCP func ti onaliti e s, wherei n the unified PDCP func tiona li tie s are used f or bot h t he master cell grou p s plit be are r an d a seconda r y c e ll group split bearer, the maste r cel l group split beare r is a use r plane bearer whose radio protoc ols a re spl it at t he ma ster RAN node a nd belong to both a maste r cell group provided by the mast e r RAN node an d a seconda ry cell grou p provide d by the sec onda ry RAN node , and the sec onda ry cell grou p s plit be are r is a user plane bearer wh ose radio p rotocols are spl it at t he se condary RAN node and be long to bot h t he sec ondary ce ll group a nd the maste r c ell group.

10. A me thod for a ma ster radio a ccess ne twork (RA N) node associat ed with a master radi o access technology (R AT), the method comprisi ng: com munica ti ng with a seconda ry R AN node ass ocia ted with a se con dary RAT an d provi ding a radio terminal wit h dual connectivity that uses t he maste r RAT and the se condary RA T; and in res ponse to recei ving, from t he ra dio te rm ina l o r a core netwo rk, termina l capability inf orma ti on indicating tha t the radio termi nal supports a spl it beare r, u sing a Pack et Data Conve rge nce Prot oc ol (PDCP) e ntit y for a maste r cel l group split be are r fo r the radio term inal, the PDCP entit y providing unifie d PDCP functi ona litie s, wh ere in the unified PDCP func tiona li tie s are used f or bot h t he master cell grou p s plit be are r an d a seconda r y c e ll group split bearer, the maste r cel l group split beare r is a use r plane bearer whose radio protoc ols a re spl it at t he ma ster RAN node a nd belong to both a maste r cell group provided by the mast e r RAN node an d a seconda ry cell grou p provide d by the sec onda ry RAN node , and the sec onda ry cell grou p s plit be are r is a user plane beare r wh ose radio p rotocols are spl it at t he se condary RAN node and be long to bot h t he sec ondary ce ll group a nd the maste r c ell group.

WE CLAIM:
1. A mast er radi o access network (RAN) node associate d with a
maste r ra dio acce ss technology (R AT), the ma ster R AN no de
comprisi ng:
a memory; and
at l east one processor coupled to the memory and configure d t o: com munica te with a seco ndary R AN node associate d w it h a secondary R AT a nd provide a ra dio term in al wit h dua l connect ivi ty that uses t he maste r RAT and the se condary RA T; and
in response to rec eivi ng, f rom t he radi o te rminal or a c ore netwo rk, termina l capability inf orma ti on indicating tha t the radio termi nal supports a spl it beare r, u se a Packet Data Conve rgence Prot oc ol (PDCP) e ntit y for a maste r cel l group split be are r fo r the radio term inal, the PDCP entit y providing unifie d PDCP functi ona litie s, wh ere in
the unified PDCP func tiona li tie s are used f or bot h t he master cell grou p s plit be are r an d a seconda r y c e ll group split bearer,
the maste r cel l group split beare r is a use r plane bearer whose radio protoc ols a re spl it at t he ma ster RAN node a nd belong to both a maste r cell group provided by the mast e r RAN node an d a seconda ry cell grou p provide d by the sec onda ry RAN node , and
the sec onda ry cell grou p s plit be are r is a user plane beare r wh ose radio p rotocols are spl it at t he se condary RAN node and be long to bot h t he sec ondary ce ll group a nd the maste r c ell group.
2. The ma ster R AN node acc ording to Claim 1, where in the
un ifie d PDCP functiona lities a re common fu nctional ities that both fi rst PDC P f u nctio nalit ies correspond ing to the master R AT and secon d PDC P f u nctio nalit ies correspond ing to the sec ond a ry RAT have.
3. The ma ster R AN node acc ording to Claim 1, where in the
un ifie d PDCP functiona lities a re a co mmon s ubse t between fi rst PDCP func ti onaliti e s corre sponding to the master RA T and se c ond PDC P

func ti onaliti e s corre sponding to the secon dary R AT.
4. The ma ster R AN node acc ording to Claim 1, where in
secon d PDCP func tiona li ties correspondi ng to the sec ondary
RAT are a subse t of fi rst PD CP funct iona lit ies c orresponding to the master RAT, and
the unified PDCP func tiona li tie s are the same a s, or a subse t of, the second PDCP func tiona lit ie s corresponding to the sec ondar y RAT.
5. The ma ster R AN node acc ording to an y one of C laims 1 to 4, wh ere in the at least one proce ssor is c onfig ured to prepare the PDC P enti ty that p rovides t he unifie d PDCP functionali ties by esta blis hing, re-es tablishi ng, or re configuri ng a PDC P entity with a c onf igurat ion common to both first PDCP fu nction a lities corre sponding t o t he m as te r RAT and second PDCP func tiona li ties cor respondi ng to the secondary RAT.
6. The ma ster R AN node acc ording to an y one of C laims 1 to 5, wh ere in
the at least one processor i s confi gu re d to est a blish, re -e stabl ish, or rec onf igure a PDC P entit y fo r an alrea dy esta blishe d ma ster cell group bea rer, or to swi tch a mode of the PDCP e ntity for the master cell grou p bearer, in such a wa y that it provi de s t he unified PDCP func ti onaliti e s, th ere by est abli shing t he PDC P entit y t ha t provides the un ifie d PDCP functiona lities for the maste r cel l group split bearer, for the seconda ry ce ll group spl it be are r, or for a sec ondary cell group bea rer, whe re in
the maste r cel l group be arer is a u se r pla ne beare r w hose radio protocol s are onl y locate d in t he maste r cell group, and
the sec onda ry cell grou p bearer is a user plane beare r whose radio protoc ols a re only located in the secondary cell group.
7. The ma ster R AN node acc ording to an y one of C laims 1 to 5,
wh ere in

the a t lea st one pr ocessor is configured to, if t he ra di o term ina l support s a split bearer, use the P DCP entity that provides t he unifie d PDC P f u nctio nalit ies also for a ma st er cell group bearer for the radi o termi nal, regardless of whe ther the dua l connec tivi ty i s sta rted for the radio terminal, wherein
the maste r cel l group be arer is a u se r pla ne beare r w hose radio protocol s are onl y locate d in t he maste r cell group.
8. A secon da ry ra dio access network (R AN) node confi gu re d t o
support a seconda ry radio acc es s tec hnol ogy (R AT), the seconda ry
RAN node comprising:
a memory; and
at l east one processor coupled to the memory and configure d t o: com munica te with a ma ster R AN n ode that supports a maste r RAT and p ro vide a radi o term inal wi th dual connecti vity tha t uses the master R AT a nd the secondary RAT; a nd
if the m aste r RAN node rec e ive s, from the ra dio te rm inal or a core ne tw ork, term inal capa bilit y information indicat ing that t he radio terminal support s a spl it bea rer, use a Pa cke t Data Convergence Prot oc ol (PDCP) e ntit y for a seconda ry cell group s plit be arer for t he radio term inal, the PDCP entit y providing unifie d PDCP functi ona litie s, wh ere in
the unified PDCP func tiona li tie s are used f or bot h t he secondary cell grou p s plit be are r an d a maste r cel l group split be are r,
the maste r cel l group split beare r is a use r plane bearer whose radio protoc ols a re spl it at t he ma ster RAN node a nd belong to both a maste r cell group provided by the mast e r RAN node an d a seconda ry cell grou p provide d by the sec onda ry RAN node , and
the sec onda ry cell grou p s plit be are r is a user plane beare r wh ose radio p rotocols are spl it at t he se condary RAN node and be long to bot h t he sec ondary ce ll group a nd the maste r c ell group.
9. A ra dio term ina l com prising:
at l east one wi re le ss tra nsce ive r c onfi gured to comm unicate with

bo th a maste r radi o a ccess netw ork (RAN) node a ss oci a ted wit h a maste r ra dio acce ss technology (R AT) a nd a seco ndary RA N node associat ed with a secondary RAT; a nd
at l east one processor configure d to:
perfo rm, via the at least one w ire le ss transce iver, d ua l connectivity th at uses the ma st e r RAT and the secondary RA T;
if the radio te rm inal support s a split bea re r, t ra nsmit , to the maste r RAN node , te rm ina l capability info rmation indi cating t hat the radio t e rmi na l supp ort s a split be are r; a nd
if the radio te rm inal support s a split bea re r, use a Pa cket Data C onvergence Prot oc ol (P DCP) e nti ty for a maste r cel l group split bea rer for the radi o termi nal, the PDCP e ntit y providing unifi e d PDCP func ti onaliti e s, wherei n
the unified PDCP func tiona li tie s are used f or bot h t he master cell grou p s plit be are r an d a seconda r y c e ll group split bearer,
the maste r cel l group split beare r is a use r plane bearer whose radio protoc ols a re spl it at t he ma ster RAN node a nd belong to both a maste r cell group provided by the mast e r RAN node an d a seconda ry cell grou p provide d by the sec onda ry RAN node , and
the sec onda ry cell grou p s plit be are r is a user plane bearer wh ose radio p rotocols are spl it at t he se condary RAN node and be long to bot h t he sec ondary ce ll group a nd the maste r c ell group.
10. A me thod for a ma ster radio a ccess ne twork (RA N) node associat ed with a master radi o access technology (R AT), the method comprisi ng:
com munica ti ng with a seconda ry R AN node ass ocia ted with a se con dary RAT an d provi ding a radio terminal wit h dual connectivity that uses t he maste r RAT and the se condary RA T; and
in res ponse to recei ving, from t he ra dio te rm ina l o r a core netwo rk, termina l capability inf orma ti on indicating tha t the radio termi nal supports a spl it beare r, u sing a Pack et Data Conve rge nce Prot oc ol (PDCP) e ntit y for a maste r cel l group split be are r fo r the radio term inal, the PDCP entit y providing unifie d PDCP functi ona litie s,

wh ere in
the unified PDCP func tiona li tie s are used f or bot h t he master cell grou p s plit be are r an d a seconda r y c e ll group split bearer,
the maste r cel l group split beare r is a use r plane bearer whose radio protoc ols a re spl it at t he ma ster RAN node a nd belong to both a maste r cell group provided by the mast e r RAN node an d a seconda ry cell grou p provide d by the sec onda ry RAN node , and
the sec onda ry cell grou p s plit be are r is a user plane beare r wh ose radio p rotocols are spl it at t he se condary RAN node and be long to bot h t he sec ondary ce ll group a nd the maste r c ell group.